Brain, I use that undo trick too, but it's useful only when I'm snapping to the grid. That's true about allowing the UV's to be a little off though, since it won't matter at the pixel level. But I'm compulsive about things like that... If you're able to write a shell snapping script, please let me know about it.
This is one thing I don't like about Maya. I should prolly put some time into writing a script to make this work. Anyway, you have to move it as close as you can. You may want to zoom in and move it again to get it more accurate. Really it shouldn't matter if you are a little off. One trick I use a lot to get more accurate…