After struggling with various networking issues with my older wireless card (the discontinued D-Link DWL-G520), I purchased a DWA-552 for $60+tx. I used the DWL-G520 for almost 2 years as my access point. But it never worked in WPA2 mode and always had problems with two (Windows) machines, iPod Touch and my Nokia trying to connect to it. I had to restart hostapd after either the iPod or the Nokia tried to connect as it would stop working.
I had setup madwifi with hostapd for the DWL-G520 earlier. But as madwifi was removed from Debian repos, DWA-552 was the only PCI wireless adapter supported by the linux kernel's ath9k module. That required me to update to the the newest kernel 2.6.30. ath9k works out of the box with this kernel in master mode.
Setup was easy as most of the work was already there. I had to setup my hostapd.conf to use WPA2 and changed the network interface from ath0 to wlan0. Restarting networking and hostapd gave me the wlan0 interface and both the iPod and the Nokia were able to detect the SSID.
Last but not the least, all this was accomplished with help from Robert's post. Thanks for documenting your experience with ath9k.
The next thing to do is to see if it will work in the N-mode. That is for another day, as I'm late to go to bed (...again) by an hour.