I upgraded to ubuntu 11.04 yesterday and played my first KGS game with it today.
It's a clean install.

While playing it looked like the stone hitboxes got a lot smaller. I had to wander with my mouse around the place where I wanted to play in order to find where the foggy black stone would appear so that I was able to place it. (I eventually lost on time)

I don't know if this has already been reported or if this is related to KGS at all, tough it only happened there.

They were hard to find, but there are a few reports of mouse problems in 11.04, so it's not related with KGS, sorry about that.