Very responsive connecting to a 400 MHz Linux box on a local network. It's a very simple app, and as far as features go, there's not much to it, but it serves my purposes completely. I had tried Chicken of the VNC, which was unusably slow (5+ second lag!), and hogged > 90% of my 1.67 GHz PPC Powerbook. I was going to give up on using VNC at all. I gave VNCDimensions a shot, and it's almost instantly responsive, and only uses 40-50% of the CPU. It hasn't crashed yet. I'm very pleased.

Works great. Would be nicer if command-tab still toggled OS X apps from Full Screen mode.