A look at how the rankings changed this month in UU. I'm looking at the top 56 UU pokemon, the current "OU" of UU.
Froslass (+6)
Steelix (+4)
Mismagius (+9)
Clefable (+5)
Roserade (+3)
Shaymin (-3)
Claydol (+6)
Staraptor (-4)
Arcanine (+12)
Raikou (-9)
Crobat (+2)
Slowbro (+6)
Azumarill (+3)
Registeel (-12)
Gallade (-5)
Milotic (-11)
Uxie (+3)
Ambipom (+1)
Spiritomb (-8)
Hitmontop (-3)
Blaziken (-6)
Honchkrow (+13)
Abomasnow (=0)
Chansey (+3)
Drapion (-3)
Typhlosion (+2)
Venusaur (+10)
Hariyama (+1)
Toxicroak (+13)
Blastoise (+8)
Walrein (-1)
Absol (+8)
Espeon (+8)
Kabutops (+13)
Magmortar (+9)
Altaria (+19)
Swellow (+2)
Ludicolo (-4)
Regirock (+11)
Rotom (-7)
Moltres (-9)
Houndoom (-11)
Feraligatr (-19)
Lanturn (+4)
Nidoking (+8)
Umbreon (-10)
Weezing (+9)
Torterra (-22)
Smeargle (New)
Nidoqueen (-25)
Electrode (New)
Sceptile (-7)
Miltank (-7)
Charizard (New)
Gardevoir (New)
Medicham (-7)
---------------------------OU cutoff
Mesprit (Out)
Regice (Out)
---------------------------Gap in usage
Hitmonlee (Out)
---------------------------Gap in usage
Glaceon (Out)
Big Winners
Altaria (+19)
Honchkrow (+13)
Toxicroak (+13)
Kabutops (+13)
Arcanine (+12)
Regirock (+11)
Venusaur (+10)
Big Losers
Nidoqueen (-25)
Torterra (-22)
Feraligatr (-19)
Registeel (-12)
Houndoom (-11)
Milotic (-11)
Umbreon (-10)
Interesting. Looks like people realized that Houndoom is easy to counter, Nidoqueen and Umbreon are a bit one-dimensional, and Torterra and Feraligatr just don't have the sweeping power they need. Apparently Steelix supplanted Registeel as Steel-type of choice, possibly for phazing ability or higher physical stats. Milotic is a nice wall, but it's just not that great.
Meanwhile, it seems UU's only Dragon type is rising. Having only two resists in the metagame is quite nice, I suppose. Honchkrow, Kabutops, Toxicroak, and Arcanine have powerful priority moves and good attacking ability, which is probably helping their rise. Regirock has...well, I don't know what it has, but apparently people like it, and Venusaur is a fairly solid pokemon, I suppose.