So you don't like Leopard? I'm a new time mac person, this is my first one I'm buying.
Not as much as I liked Tiger - but trust me, even with my issues with Leopard, it's worlds apart from PC. Most of my issues are cosmetic, and habit-based. As a newcomer, these likely won't even phase you.
General consensus is, most of the issues us Tiger folk have migrating, will be resolved within a revision or two. (10.5.2 or 10.5.3)
Honestly - I used Apples WAAAAY back in 92, did genuinely like it, but left because "everyone else" was using PCs.
After using PCs, knowing how to wipe, format, install, reg edit, update and roll back drivers in my sleep from doing it so much, I realized I was losing valuable time.
My PC died (physically), and out of desperation I went to the first computer store near me - they happened to have Apples. I had no interest, but figured I'd look at one considering I drove there. Walked out with an Imac 20 minutes later.
For almost 2 years, I haven't had to wipe my drive or OS between 2 Imacs, haven't spent a cent on Antivirus / Firewall / Spyware or "Speed Optimizing" software.
I also run XP native in bootcamp (because plenty of apps I do need there), and in Parallels within OSX.
All in all, a positive experience. Just if you grab an Imac - I'd say opt for a decent video card, as the hard drive and ram can be upgraded fairly easily down the road - video not so much.