I'm an RD guy, myself, but I've always heard that the GT750s are very solid and reliable. There are several that keep on coming up on my local CL for short money. It's tempting, but I just can't get that enthused about a 550 lb bike. My RD350 is just under 300. The GT has a reputation as a good long distance bike, which my RD certainly isn't. Go for it!
I wouldn't bring her home to Mama, but Mama ain't home tonight.