For the record, I've had similar issues in WebOS. I think it's flaw in the wireless chip or a driver bug that exists in both the WebOS and the Android version.
Ehh? Wifi on Android with custom ROMs is an issue especially when good drivers aren't available. A good tip when you have wireless issues is to delete the wifi_supplicant.conf file in /data/misc/wifi/ or whatever. It lists all your wifi networks and a few scanning parameters along with the passwords. Delete and your phone will work a lot better.
I noticed this on my SGS2. The wifi struggles to connect to my router at home and my gf's router, but at work its fine. I deleted the file and now I'm able to connect effortlessly to all my wifi networks.
CM9 on the TouchPad is no exception. It acts significantly worse. I am not aware of any wifi problems on webOS but in general wifi problems are the biggest problem on ANY device. 95% of the time its the router. Some routers bog down over time and need a power cycle. So I'm not sure if say webOS for the TouchPad has more wireless issues than say a good working iPhone 4S. I hop around enough wifi networks to notice that my SGS2 has issues on custom ROMs (stock is fine), and my TouchPad has issues left and right on Android, but on webOS I haven't had any issue yet.
A new driver could help certainly.
Finally, you guys should just skip Alpha 2 and jump to any of the nightlies. I know people aren't super comfortable with nightlies, but they have newer kernel merges and stuff. There's a lot more things working like battery icon and stuff with the new boot animation. I think its worth trying out at least. I've been on nightlies since HW acceleration was merged in.