Just jumped back into UU since the Cresselia/PorygonZ period, and this has definitely been one of the most fun phases of UU I have ever played. After the tier has settled a bit (meaning no more Rock Polish Steelix users), there seems to be an incredibly stable metagame that still maintains its diversity and unpredictability. A few observations:
For the major Grass types of UU, Venusaur, Sceptile, Torterra, and Tangrowth, there are about 3-4 completely viable sets for each of them, and people have been experimenting more instead of just SD Venusaur, Mixtile (who can still run like ten different moves), Rock Polish Torterra, and physical wall Tangrowth. Venusaur have been running around with Scarf sets, special sets, physical tank sets, special tank sets. I've been using Subpunch Sceptile lately, and it kicks ass. It works especially well with heavily special teams, who need a great Chansey/Registeel lure. Torterra is scary as hell to face, especially sets with Substitute. Tangrowth has been sweeping with Sunny Day sets and walling nearly every physical attacker. Grass types in UU are among the most versatile pokemon ever.
In relation to that, it seems as though just about every pokemon in UU has about 4 different sets, all totally usable. Even Milotic is stupidly unpredictable. This definitely wasn't the case in the Cress metagame.
With its wide movepool, good attack stats, and speed, Mesprit has been working as a wonderful safety net vs. just about any threat except for faster ghosts and dark types. It also helps a lot against balanced and offensive teams, checking threats and spreading paralysis really well. It seems similar to CAP's Krillowatt.
It also seems as though people have given up trying to make Cloyster, Omastar, and Qwilfish work as Spikers to fulfill Froslass' role, and are shifting away from the spikestacking teams to more conventional team archetypes. Spiker + Double Ghost is a bit too much to ask for for many teams. This is definitely a nice thing to see.
The lead game is pretty crazy as of right now. Not too many of anything. What have you people been using? I've been using 227 speed, max special attack, rest in HP Venusaur with a special attacker set that catches a lot of stuff off guard. Choice Scarf leads people to play against lead Venusaur a specific way, and non Scarf Venusaur gives people a lot of trouble.
EDIT: Milotic's a bitch.