If you want a quick glimpse into my rating system and what I've seen (as well as the new weights), the list is here. The primary changes on this list are that armor pen is increased slightly, haste is increased and crit is decreased. Again, do not use this list without some intelligent decisions; hit and expertise aren't that great when you have hit the caps, don't go overboard on arpen if you're at the cap...basically, be mindful of those caps I talked about earlier.
Speaking of, here's the first conclusion from what I linked: the armor pen cap of 1400 is going to be what most people should seek out, as a hard cap. With simply taking everything in slot that was agi gear and which had armor pen, and not optimizing in any other way (no hit/expertise), and not doing anything with gems - you can get using the above listing a total of 1270 armor pen rating.
That's before food buffs and before any gems. Adding gems to that would result in somewhere around 300 more armor pen, depending. And this isn't with a full set of known gear, nor is it with a full set of heroic gear. I will confess that it has some sweet gear in there - Deathbringer's Will, the full heroic Lasherweave set - but a bunch of that gear is also from ToC.
Point being is that it should be pretty obtainable, and certainly something to strive for.
The problem here is that with the new Needle-Encrusted scorpion that drops from the heroic 5-man, you're kind of encouraged to drop armor pen hard capping. From all the tests I've seen hard capping is the way to go...but that means you'll want to use the scorpion or runestone until you get enough arpen gear to switch.
So when should you switch to hard capping? I would argue that it's probably reasonable to do so when you obtain that awesome trinket. If you don't get Deathbringer's Will, it's going to be hard to cap for a while. If you don't have Death's Choice either, then you're trading down quite a bit. I haven't run the numbers and don't have a perfect value for you here, but for me personally I'm planning on switching when I can reasonably get to 1100 armor pen. I will try and figure out exactly what the cutoff is, and post it to you.
In any case, it's going to be a while before that needs to be decided anyway. So plan on grabbing armor pen where you can, try and get older pieces with it just in case, and in the meantime go for the softcap.
The second point is the hit/expertise issue. As I mentioned previously, the expertise and hit on leather gear looks...pretty sad. Or at least looked; one piece of tier gear got changed to have expertise on it.
There's no hit on any piece of tier gear. In fact, the total number of items in 3.3 that are druid-friendly and have any hit of all is...only 18, at least so far as we know. And of those, three are one-hand weapons. Sigh. So there are 15 items total - and most are rings. Only 4 known ilvl 264 (that's normal mode 25 man), and only a couple decent rings. So hit is going to be in short supply. That being said, this sack of wonder is going to be a boon for a lot of cats and bears, I think. The issue is that this conflicts with the high arpen on the tier pieces. Sigh.
So just looking at the non-tier slots, you can get a decent 10-man cloak, a 25-man ring, a rep ring, an okay neck...and that's about all of any significant ilvl. Which would add up to 206 rating.
So chances are that optimally, you'll want to get at least one nontier piece to have reasonable amounts of hit/crit. Another solution is actually to go with the much-maligned Grim Toll; the hit will give a better return than higher crit will, and the slightly lower arpen will allow you to get more out of the arpen on the gear you want.
Expertise is, as mentioned, a bit easier to get. The tier legs have expertise now, there's a good set of crafted boots or a bought chest via emblems- basically, things you might already want to get. Since the cap is so low for expertise anyway assuming you're taking primal precision, it shouldn't be hard to hit that cap with one or two pieces at most. I personally would likely go for that 10-man cloak and that wonderful sack.
The tier bonuses are worth talking about too, and for the first time this expansion I'm going to utter the phrase "Get the tier pieces ASAP". The 2-piece bonus is decent but not phenomenal; a savings on your finisher is good, but on average this will save you about 30 energy every minute at best. That's an extra shred every 80 seconds or so, which is good but nothing that you'll freak out about.
The 4-piece bonus is worth freaking out about. Rake critting will add an additional 60% damage at icecrown levels of gear (because you'll be critting 60% of the time, most like). Since Rake accounts for roughly 10% of your overall damage if you're doing a good rotation, this is essentially a 6% upgrade in DPS by itself. That the tier pieces are magnificently itemized for cats is also a bonus - but really, you should be going after the tier pieces ASAP.
In case you missed it, you need to get the beginning level tier piece before you can get the 25-man piece. Which one you should get personally is going to be heavily dependent on the rest of your other gear, but the legs rank the highest, followed closely by the chest and head. The 251 chest is a slight downgrade from the offtier piece in ToC, the gloves are a slight downgrade from the Sunreaver assassin gloves from heroic ToGC 10, the head is better than anything in ToGC, the legs are a slight downgrade from the offtier piece, and the shoulders are a slight downgrade from the heroic 258-level tier piece. Based on that alone, I'd say get the head first, then the shoulders, then the gloves and then the legs - but you should do what makes most sense to you.
The other thing to spend your emblems on is this amazingly awesome belt. That's not hard to be that awesome given that it's the only belt so far found in 3.3, but it's very good for cats and one of the very few belts in the game that has armor pen on it. I wouldn't get this before getting your 4-piece, but it's certainly something to save up for.
The new idol is also out, and it's...I'm not thrilled. In theory this is going to be 10% better than the last idol at full strength. The problem is uptime. Any fights where your rake will regularly drop off (the proc only lasts 15 seconds) and this becomes a compounding problem on the cats' already problematic long buildup time. On stationary fights this is good, but any time you're dealing with multiple mobs (so not raking much), any time there are phase changes, any time there's a lot of movement...this is not as good as other options. For the first few weeks at least, the fights consist of a tank&spank with a phase change, a ton of adds, a ton MORE adds, and then finally Saurfang - who may be a tank& spank kinda. That doesn't scream "OMG spend badges to get 20 more agi sometimes" t0 me. So wait on it.
Finally, on weapons - only one really awesome one has been found, and that's Distant Land. It has 3356 Feral AP, in case you didn't find that out yet. Lightborne Spire is the quest reward for the long Quel-Delar questline for ferals, and it's certainly good - but it's better for bears than cats. I actually think I'll hold on to my Twin's Pact for a bit; the arpen is going to be valuable. I also believe that there are going to be a lot more options here soon. Heck, not a single polearm has been found. My gut feeling is that these haven't even been made yet, and they're waiting or working on them as we speak.