Well, I've been working on Leopard since sometime Wednesday...ish.... Really, I've not had a TON of time on it because I am trying to be VERY selective in what I move over from my old machine. So far however it seems to be kicking butt! I probably won't buy it for home yet, as many of the updates appear to be far more beneficial for productivity rather than say... play time. But like I said, I've not really been into the deep workings of it yet.
I have noticed a couple of buggish type things like random freezes requiring a restart (UPDATE* apple has identified this and is officially working on a fix), printer errors (no big surprise... efi seems to have those often), ichat errors, and a few personal preferences that are not exactly how I want them. For the most part however, it LOOKS BEAUTIFUL!!! seems to function very well and I am looking forward to the complete switch over. I'm kinda leary of installing CS2 with the impending install of CS3 in a couple months. Mail looks to have had some serious upgrades, and iCal is working fantastic!!! Preview is killer, and quick look is unreal!!! Overall (so far) I'd give it an 8 and recommend it to everyone using a mac (or a PC :-).
