Hi Steve,
As the most recent convert here I'll give it a bash. I think a lot really depends on what you mainly use your computer for, what programs you have that you consider essential etc. Bear in mind that anything with an exe.file no workee on the Mac, so for games etc you'll be up for replacement software. If on the other hand you mainly use it for internet and office applications etc, the process is fairly seamless. I found it was worth buying the Office for Mac, but that should be the only software you need on top of what comes with it. For music, graphics, photos/movies, etc, it would appear to be beautifully integrated and much more user-friendly than Windows.
As far as major differences are concerned, there aren't really any of significance. There's a lot of little things that are done differently, and a few that take some getting used to. I've had some problems (still am in fact) networking with the PC, but I'm 100% certain it's a PC problem not the Mac.
There is a great package of software that comes standard, including things I haven't even tried yet. As I mentioned elsewhere, some of them look superb but are somewhat restricted in their use with people using Windows.
In terms of the overall computing experience, they're a marvel. Very instinctive and with some delightful touches that make Windows look horribly confusing and clunky. I'll be buying a lappy in a couple of weeks, and after three months with the iMac there's no question I'll be staying with Apple.
In simple terms, if everybody had a Mac the computing world would be a much nicer place. But most don't, so if you elect to make the change, get used to the idea that there will be the odd irritation with non-compatibility with M$ products and the occasional lack of Mac versions of something you want (the Webshots desktop comes to mind).
I won't unreservedly recommend them, because it depends on your own requirements, but I am an enthusiastic convert. You can keep the old PC for Windows apps that you simply must have; I did, but I find I never use it except when I can't get my daughter off the Mac.
As a final point, if by chance you get one and find you don't like it, a quick look at ebay will tell you that the resale value for Macs is terrific! This a great place to come for help if you need it too.
Let us know what you decide.