I can not say much because I have flashed directly after receiving DD-WRT on the original firmware unfortunately. So I can not judge how to cope with it lay. The price / performance ratio is really great!
// Addendum:
When loading a 100 MB file from the local NAS (via FTP) the following values:
NAS> LAN> Wireless> MacBook Pro: 9 Megabytes / s (approximately 72 Mbits)
MacBook Pro> Wireless> LAN> NAS: 10.2 MB / s (approximately 81 Mbits)
Please note: Without a router to wipe the NAS creates about 35-40 megabytes / sec.