I haven't used gnomes, but I don't think that's really the point.
The question shouldn't be, "have you used gnomes," it should be, "are gnomes usable?" The first might shed light on the second, but it isn't everything.
I don't think gnomes are particularly usable as they currently stand. Gnomes have four things going for them.
1: Small size
2: Artificers
3: Illusionists
4: Bards
Here's the problem with that.
1: Small size doesn't help you be an artificer, illusionist, or a bard. It helps you do stuff that halflings are better at anyways.
2: Artificers are a nice idea, but the game hasn't got any rules for techno/magical artificing. The Eberron "Artificer" class is as close as it comes, and that seems to be staying campaign specific. If you want to be a gnome who does something gnomish, perhaps designs a high tech magical crossbow monstrosity and shoots things with it, you really can't.
3: Illusions are kind of weak, and also don't fit with the artificer theme.
4: Bards are kind of weak and are getting seriously revised, and also don't fit with the artificer theme.
So I figure, drop them from the core rules. Revisit them at some later date. Give me a gnome who can build himself a steam powered hammer and wears high tech goggles and boots, and I'll be a happy gnome player.