Very slick, overall I like what I see, with a few exceptions.
Let's start with what I like:
> I can see boosts on mouseover (e.g. if I have 5 CM's I can see +5 +5 on SpA and SpD when I mouseover). This means I don't have to keep track of how many CM's I've used or how many times my SpD has been reduced in comparison, etc; very helpful.
> Moves are colored by type. This makes misclicks a tad easier to avoid, and I'll take what I can get.
> Moves I can't use are unable to be selected (might also be slightly greyed out, only happened once when I got taunted so not sure). I prefer this to being able to select but not use.
What I don't like:
> I can't display % health on my poke's HP bar. I appreciate being able to see the % in the battle log, but it's really not as meaningful if I can't see % remaning on the HP bar as well (and I'd rather not calc every time). Adding options for raw HP display is nice for those who prefer it, but the toggle option should be extended to the HP bar (and to mouseovers on the opponent's pokes instead of the xx/48 which is actually less accurate than %).
> Field effects don't seem to be displayed on mouseover anywhere (e.g. SR, Spikes, Toxic Spikes, Gravity, Trick Room, Screens, etc). Only some of these displayed in Shoddy, but I'd really love if all of them displayed as well as how many turns remained on them (at least for your own Screens, I can understand not displaying how many turns remain on your opponent's if they want to bluff light clay).
> Pokemon type is not displayed on mouseover. This isn't really an issue for me now in Gen IV, but when I'm still unfamiliar with Gen V looking up constantly will be annoying.
> Opponent's timer does not appear to countdown when I'm waiting for them to make a move. It does indeed go down by the time elapsed when they select a move, but I can't see it countdown; so it's easy to lose track of how much time they actually have left.
> Find is not immediately obvious. If challenge gets a button, shouldn't find?
Also there's no rating system or UU yet, but I'm guessing those are some of the reasons it's in "beta". Again I like what I see and look forward to seeing it improve in the future.
Edit: Another thing I wouldn't mind seeing is having HP's displayed with their actual type/color. I know the actual game doesn't, but it would be nice and I don't really see how it could hurt.