Unity isn't that bad if you have a decent machine. There was progress in the first month. The big fix they did in the first month was the click-through.. can't think of the word for it. The one where you clicked with your mouse on a dialog and then something underneath got the focus, when it shouldn't have. That was fixed pretty quickly, definitely in the first month.
There are a few drawbacks.
1) If you are on a hi res monitor (I'm 3456 x 2160 on a 15" display) everything is too small even at max UI scaling. Also at max UI scaling (200%) some features are unavailable (e.g. "trade" menu option when clicking on friend in friends list).
2) Gen context switches. Gens who lose focus during battles can't be retreated. Gen context switches when another gen gets focus, which makes sending the correct gen difficult. What that means is, things like, you have to wait for everyone to finish moving before you send another wave.
3) There are UI issues where buffs/gens appear greyed out in star but can still be used.
4) Gens/buffs occasionally will show the incorrect icon in star. I'm sure I don't have 4200 General Tremble Beards that mouseover reads, Gift basket.
5) UI issues with buildings showing upgradeable when they are not
6) Deposit icons/text missing until you mouseover them.
7) Don't even try to look at production values for a particular building. Crazy numbers.
8) Many string interpolation bugs.
9) Performance lags the flash client.
That's the worst of it.. don't seem to have much of a problem other than those big ones. In short, it's definitely playable, but not quite as much fun.