I've got a DecalGirl skin on my Kindle2 and my Moto Droid. I found them surprisingly easy to put on. The first Kindle skin went on perfectly the first time. The second one, I didn't have it lined up right and had to pull it off and start over. The only issue with that was that it had stretched a little, so it was a little "big." After smoothing it down real good, it shrank back to its correct size and looks great.
I'd definitely buy from DecalGirl again, except that I really love the skins I have now and can't see myself changing anytime soon.