This usb card AWUS036H coming from alfa network is a jewel!. She's fully compatible with aireplay-ng, 500mw, a RP-SMA connector and -96dbm sensibility !High security 64/128/256bit WEP Encryption, TKIP, WPA, 802.11.
She've a realtek rtl8187 chipset, who works great under linux and with the aircrack suite.
She has a RPSMA connector too and she's more portable with no usb wire need.
This time, it's not a realtek rtl8187 chipset but a ralink rt2500 chipset, much better ;)
Also works great in WEP and WPA TKIP/AES see the constructor doc for more informations.More of then , with her ralink chipset, she's really good supported by linux and especially backtrack.