I've been dual-booting XP and Ubuntu for about a year w/o any problems. I came across Mint and my first thought was that it really looks good. I decided to install it in the Ubuntu partition. Since the dual-boot was running so flawlessly on the desktop (and a laptop), I thought this should be an easy one.
This computer has a SATA primary drive, and I had stuck in an old IDE drive as a backup (long before I installed Ubuntu). When installing Mint, it decided that the IDE should be the primary drive & the SATA the secondary and apparently wrote that to the MBR. It took me a while to figure out what had happened, and another while to fix it. I was down for about a day.
I would guess that this is covered in some documentation somewhere and I should rtfm first. But I didn't. Just thought I'd mention it. All in all it was pretty troublesome.
Mint does look good though.