I’m not really a fully paid up apple fanboy, though you would have to prise my Macbook Pro from my cold dead hands. I have now installed Leopard, aka Mac OS X 10.5 on both my PowerPC based desktop and my intel based laptop. Both upgrades were a doddle really, and I would say I was pleasantly surprised that all 3rd party apps seem to be functioning as normal. I have heard reports of some issues for some people in the Nominet HQ. Also it seems like if you have partitioned your hard drive with the boot camp beta you may not be able to do an upgrade, but only a wipe and install.
I have to say though Leopard really is only an incremental improvement on Tiger, I’m quite liking the spaces, but I already had this functionality on my desktop thanks to codetek vritual desktop. I’m not convinced by cover flow in finder, it seems to take longer to find things with this.
For me the killer app is time machine, being a dba backups are close to my heart, but imagine my disappointment when I realised it was not going to play ball with filevault. So, really not all that worth the £85 for an upgrade, but boy am I glad I don’t use Vista!