Not bad
I think the game only glitches if your computer is an absolute pile of crap. I have Vista x64 and I'm running Chrome. I'm basically doing everything wrong compatabilitywise and it ran fine for me.
There are three things that I think would make the game a lot better.
The first is physics collisions. People getting slammed up against other people, etc.
The second is a MUCH larger playing field. Maybe 5x as big. This would make the physics work better and present more of a "carnage factor" (assuming you also quintuple the population).
The final one is what everybody's asking for: ramping difficulty. For the last ten levels I limited myself to only buying Gravity Bombs and even that was so easy I had to let myself die.
Aside from that I'd say the game is enjoyable for 10 minutes or so but after that you've seen all there is to see and the game holds no more interest for you.