I've done pretty extensive comparisons between one of the old Airport Extreme Dual Band units that look like a white Mac Mini and run some flavor of NetBSD and it performs slightly (~10%) better than both my old WRT54G and superior-specced WNDR3700 running DD-WRT builds. I still use the WNDR3700, not for performance, but for features and configurability. The APE basically just sits and serves a network disk.
