After having the inspiration from my pineapple, I played around with AP121U a couple of months ago and this was the result:
Some experiences as much as I remember: dumping wired traffic to USB and having access via WiFi (smb/ssh/ftp etc.) worked very smoothly. Web mitm along with dnsspoof, tcpdump, ettercap etc... The performance was up to 40-60mbits while tcpdump'ing (if I recall correctly). Possible to use for VOIP pentest with appropriate tools. Also set the reset button to a default connectivity options for recovery (was easy to kick yourself out accidently while massing around). Wireshark, Cain, networkminer etc. can analyze the dump via smb during tcpdump if you connect a Windows via Wifi, otherwise backtrack is your friend for the rest anyway. As far as I remember only sslstrip caused memory issues. Beside that it was possible to implement various scenarios.