Painted black here. Wish I didn't do it now though and went the way I did for years - black paper.
Reason? Like a dummy, I left the magnetic cleaner in a what I thought was a good spot on the top of the tank (still ready to swipe and clean). You know where this is going.... Kids decided to help dad and clean the tank, got some eco-complete in between the glass and the scrubber and scratched the crap out of my tank. BAD. I mean really bad.
Had I had paper back there, I'd just drain, rotate and have a nice new surface, relatively free of scratches. Now, I have to drain, dismantle, use stripper and make one hell of a mess.
The paint looks better for sure, not even marginally, but significantly, in my opinion. If you ever want/have to remove it though, bummer....