I'm actually in a similar position... I have a pretty high spec self-built Windows desktop and am buying a laptop soon. One of my housemates swears by Mac and pretty much everything about them. Personally I don't like how OS looks and works... which is something alot of mac users seem to bigup so to speak. Some macs look nice in my opinion, some look awful, but that'll vary from taste to taste.
Something I'd suggest you consider is having to go between your Windows Pc and the Mac... that would do my head in eventually I think, I know macs are apparently not as incompatible with windows pc's as we think but from my experience they actually are (awaits slating....)

From the simplest things like bluetoothing a file from my pc to my mates mac turns into a drama these days... or if I size up some images in photoshop and occasionally have asked him to print them for me... he'll open them up and they go all stupid on his mac, it seems to just disregard everything I did with the images on windows, its so frustrating. :x
For me it has to be a windows laptop, mainly based on the fact that a major program I use AutoCad... is windows based and sure as hell I ain't spending a wad of cash on a mac to buy some crap PC emulation software... sorry but what on earth is the point in that? :madmad:I've seen Virtual PC trying to run imaging/design software, god it took about 7 minutes to open the "file" toolbar. It was embarrassing....! Like someone said, emulation programs are incredibly slow... why you'd want to buy a mac then spend 150quid turning OS into Windows I'd never know, but, if you were going to and wanted it to run very smoothly you'll need a pretty good mac.
Don't get me wrong, macs are very nice indeed and for the right person I think they're great, its probably just down to personal preference... it might be a good idea if you can find a friend with one or have a play with a mac in a store just to see if you like the general feel etc.
The general opinion is that macs are great for video/imaging/everything graphicy... I dunno about that these days like someone else has already said... things have changed!!
One thing I will say in their favour is the lack of viruses circulating...... pity about the fact that I think they're hugely overpriced for what the money would pay for in the windows equivalent!
Anyhoo... good luck deciding!