Only after I got that 1 TB external.
No more worries - plug it in, forget about it. (in OS X, at least. For Windows, I'll just manually initiate a backup if it's over the scheduled time - once a week)
I have the disk partitioned into three parts - 250 GB for Time Machine, 250 GB for Windows Backup + Windows Image Backup, and 500 GB for general storage. The general storage partition uses exFAT for read and write compatibility on both Windows and OS X.
Oh, and the Mountain Lion upgrade went off without any hitches, aside from the SkyDrive application stopping working. No problem, since I deal with SkyDrive more in Windows anyway. And $20.