I'm running art out of curiosity. everything is working fine, no problems at all. but honestly, I cant tell any difference between art & dalvik in terms of speed/battery life/whatever. the only noticeable difference is the longer boot time with art. I do not keep track of ram usage or do any speed tests or details like that. Maybe there's a difference on that level, but it's not perceptible as a user, imho.
so, at this time, is it worth switching over? eh, not really. doesnt matter much.