I looked into it once and read that the print holds pretty good. I'm just too cheap to spend $100 to camo one rifle when I could get something half way decent for $15 out of spray cans.
I love the idea of camo rifles, but if you do this just plan on keeping the gun for forever. Used guns with "homemade" camo or paint usually don't go up in resale, at least from what I've seen.