I've had the Quickfire Rapid TK for three months, and it's a great keyboard to type on. The letters themselves show no sign of wear, but the textured top is definitely wearing smooth on the commonly-used keys (like so: http://commons.wikimedia.org/wiki/File: ... attern.png
). It's not nearly as bad as that picture, but it's something to consider if your user is bothered by the aesthetics of the keycaps.
(I use the same keyboard at work and home, cleaning with alcohol wipes, so it may be wearing quicker than it usually would)
Still, I'd recommend it anyway since the WASD keycaps are compatible, which should make for easy replacements in the future.