Here's a breakdown of the highs/lows for me compared to Tiger:
- Spotlight performance: +1; (usable!)
- General OS responsiveness: +1;
- Safari Speed: +1;
- Safari Reliability: -1; (has crashed on two different web sites for me so far! -- guess I'll go back to my camino/firefox combo)
- Quicklook: +1;
- Dock improvements (grids and fans): +1;
- Time machine: ?; I set it up, but for me the jury is out on any backup software until I actually need to restore something.
- Haven't found any major app incompatibilities yet.