I can see what they're trying to do, but they're both unusably horrible on this machine (dual quad Xeon Dell T5500 running Fedora, Chrome 17). The pen / path tool just didn't work for me in Picozu, and the smudge tool in pixlr stutters and locks up the whole interface (presumably while it pushes pixels around).

I can't say I'm convinced by web paint programs. Maybe OK for a trivial "fix-my-redeye" case on something you've already uploaded. I also wish these things would stop claiming to be Photoshop clones, when they're really just MS Paint++. I used to use PS professionally (ie. I've earned money with it to easily justify the initial outlay and upgrades from 6 thru CS5) and there really is nothing to compare it with.