Wow well I personally find a lot of this stuff interesting. Looking at pokebank ubers first, I wanted to draw attention to #1. Chances are, if you play pokebank ubers, you run a Xerneas. Now, every single time I have seen a Xerneas in the tier, I sent out my Ho-oh to counter his ass. Even after a Geomancy boost, Ho-oh w/ Sacred Fire wins out one on one (I run recover too, in case I get critted). And while I know Antar's 'checks and counters' disagree, Ho-oh is always first to come out and counter MY Geomancy Xerneas as well. I'd really like to see HP [Rock] on Xerneas a little over Flash annon, dealing with Ho-oh easily and also smacking Shedinja, a common counter which can be troublesome for Hyper Offensive Ubers teams. (If there's something Flash Cannon hits that Xern's other moves don't, please let me know, I'm curious.)
Something else I wanted to comment on is the fact that Antar said Gen 4 OU resembled Gen 5 UU quite closely. I look at all the pokemon which are on their way to getting kicked out of the top 50 and can't help but imagine that the same will happen to this generation. Some of the speedy but not-so-powerful mon's (Jolteon, Duggy) or slow and strong (Reun, Metagross) are outside the top fifty and don't really look to me like they'll be making a comeback when Gen 6 settles down I think this gen's lower tiers will look really interesting.
Otherwise, Rotom-W has quietly climbed to number one on the pokebank usage lists, being a nice counter to lots of common threats like Talonflame, and being weak to only Grass and Mold Breaker Ground moves. Roselia brings some potential to take it on w/ Natural Cure (as was already discussed, I know) and set up Spikes. Scolipede is another much-discussed new potential 'mon, and I think the Swords Dance set works great, if you can get an opponent to switch out as you get a speed boost and doubled attack stat, you're good to wreak havoc. Unless the switch was to Talonflame, in which case you need to kiss your ass goodbye.
New account, first post, please don't be too hard on me everyone :p