I agree that getting an Intel-based Mac laptop and dual-booting or using a VM seems the best way to do this. You'll have the added bonus of having access to all of your programs and all of your files wherever you go.
Yeah, the more I think about it, the more I agree that this is the way to go. I guess my reluctance stems from the fact that Boot Camp (which I would use rather than Parallels, as I'll be in Windows most of the time and in Mac mainly during the evenings and weekends) is still in development and I've heard stories of people who've run into occasional compatibility problems. But those problems are mainly with hardware, and the only things I ever connect to my Windows laptop are a monitor, a REV drive for backups, and a jump drive. Shouldn't be any problem there.
It won't save all that much money to go with one machine, however. I priced out the MacBook Pro that I'd need (with a larger hard disk to hold my work-related files as well as all the photos and music that I keep on my Mac) and it comes out to over $3,000 Canadian, plus I'd have to purchase Windows XP on top of that. I might also have to buy a new REV drive, because mine is a first-generation one that doesn't work on a Mac; I'm not sure if it would connect through BootCamp or not. The REV drive is good for me as it's the best solution I've found for offsite backups; I can put 35 gigs on a disk and hand it to my girlfriend to store at her office.
One of the things I like about having two computers is that I always have a backup in case one computer dies or has to be serviced. But my girlfriend has an IBM laptop that I bought for her and I can use that as a backup. On a minor note there's also the keyboard issue: most of the time the laptop will be connected to an external monitor and keyboard, and I'm not sure how the mappings work if I use a Mac keyboard for Windows or vice versa. Does the option key on Mac translate to the Alt key on Windows? And what about the command key (the Apple key)?
When it comes time for me to upgrade Office--which won't happen for at least several more years, as I use Office 2003 and none of my clients or colleagues are planning to upgrade to the 2007 version--I will look into OpenOffice. There's no reason for me to switch now as I already have Office and it's not costing me anything.
Thanks everyone for the feedback and thoughts!