I have made the leap. I finally installed Leopard. It's a little early to say if I like it just yet. It is different. Spaces is a little in-between for me, but I am very happy with Stacks. I'm gonna do a little mini-review on Safari since I wanted to do one for Safari 3.0, but never did.
Well, I wanted to praise Safari's improvements of having functional tabbing. Safari 2.0's tabs were pretty terrible, but the improvements in 3.0/3.1 have made up for it. The tabs are now draggable, and "pull-out" feature of being able to turn into new windows and vice versa, pulling tabs from other windows and transferring it into another Safari window is just phenomenal.
I guess for functionality that's it really. But the most important thing is the jump from 3.0 to 3.1. The SPEEEEEED! Apple boasts about it on the site, but they are not kidding. It just renders everything on screen faster.
Firefox has taken a backseat now. I didn't have a choice before and needed it to run my Gmail so I could use Googletalk, but Safari/Webkit's upgrades have made that functional. Now I almost use Safari exclusively, except for when I need to do browser tests. Or when Safari crashes.... which seems to come a bit more often than usual.