I just finished painting my bathtub a couple of days ago. I used Rust-Oleum Tub & Tile Refinishing Kit, and it's still curing (you're not supposed to get water on it for three days), but
the paint seems very durable. Of course, it IS paint, so it won't last forever, but I think this is a very good solution if you want a somewhat easy fix for an ugly, outdated tub, and don't quite have the budget for a complete replacement. More details (including a video) at the link below.