Personally, I would stop by your closest Apple store and play with a MacPro and the new iMac. Maybe even take your camcorder with you, plug it in and see how easy it is. Ask them about Final Cut and Aperture.
Next, go to your PC store of choice (Best Buy, CompUSA, Frys, whatever) and do the same on a new PC running Vista.
Which one do you like? Which one is easier to work with on drivers, color matching, RAW support, etc.
Compare the cost of an iMac 24" to a comparable PC, insure the PC has a DL/DVD drive 256MB video memory and is also dual core. Or, compare equal Dell/HP/whatever to a MacPro if you prefer...or perhaps a MacBook Pro.
To keep things fair, factor in the "upgrade"/conversion price for any PC software to get Mac software. This is where the Mac could lose since you have existing software thats paid for, I don't know what Adobe charges for the conversion but I know its possible. Also factor in the cost of an OS upgrade, assuming any PC you buy today will support the next version of Windows...so add maybe $200-300+ to the price? Mac OS is typically $129 for a single pack or ~$199 for a "family pack" (up to 5 computers).
If you decide Mac, buy it next month and get Mac OS X Leopard.
Personally, I am not a fan of Vista and think its a serious regression in usability vs XP, there is a reason MS has extended the time period that XP will be available for purchase. I have worked in IT for quite some time and make money off of MS products, but I avoid them on my time as I want something that just works without the headache.