I can't say I was a fan of this style of scrollbar on Tiger - it just looked out of place. Having said that, it rocks on Leopard! (Although tbh I'll probably switch back to the Aqua ones eventually)
<Off topic>
I'm really enjoying Leopard so far. It seems very polished and has just a nicer overall feel than Tiger. For example, the network pane of Sys Prefs on Tiger seemed a bit outdated but its been vastly improved for Leopard. At the time, Tiger was very good but looking back it just looks old, outdated and, to be frank, pathetic.