The Flightstick is made by Hori, which is itself is basically a Saitek stick. It works great with AC5, and I know jack about the drivers for the stick for the PC. I know it can be done, as people on the AC forums on both AC net and the official site have used them.
Yes, it's pricey, almost $80...but nothing beats it if you want to play AC5 (or AC4). If you think it's too pricey, just get the game and use the Dual Shock. Haven't seen anyone who bought the bundle gripe about the stick though...you get the game, stick, and a huge Wardog squadron flight patch big enough for a jacket. (If you pre-ordered you got the tin with patches and preview DVD).