I much prefer Macs over Windows PCs because of the OS; Mac OS X is just way better than Windows whatever, in my reasonably humble opinion.
It might seem that most people say Macs are crap, etc, but that's because most people do, as most people have Windows. People always say 'this' is crap, if they have 'that'.
Anywho, back to the real topic!
Unless you really want to carry your computer around, I'd wait a few weeks and get the slightly upgraded mini.
As far as I know the lack of core image only means it can't do the super snazzy, yet pointless visual effects. I could be wrong though..
And I think they've said it'll be late next year when they start to move to intel, so whatever you buy, it'll be a while till it's behind the times, so to speak.
Or if you haven't already got a monitor (pretty unlikely..), get the eMac.
And just remember, the more RAM the better. It makes way more difference than the extra ghz. 512mb's been fine for me, but if you want to use all those apps at the same time, I'd go for 1gb.
Also worth a note: You can use USB meese on Macs, so that means any 7 button microsoft whatever.