Registered just to post this in the hopes your issue can be solved.
I had the same problem. I use my TouchPad almost exclusively at home, on my own private network, through an ASUS Wireless-N router running DD-WRT.
Since installing Android [specifically CM9's 3/29 official nightly], I was consistently getting dial-up speeds while all other devices in the house screamed.
I searched for days for an answer, installed alternative wifi drivers, tried FXR Wifi from the Market, and nothing helped or hurt the situation. For consistency, I restored back to original nandroids after each attempted fix.
What finally DID work, and was suggested for a similar but unrelated problem on a different site, was changing my router's network mode from "Mixed" to "BG-Mixed." Suddenly, even though I had ostensibly disabled the faster Wireless-N protocol, my CM9 TouchPad boasted near-instant page loads across all apps.
The best part is that I have since restored the router to "Mixed" [i.e. reactivated Wireless-N], and the high speeds remain. Apparently performing this momentary switch was the toilet handle-jiggling that this problem needed.
Good luck, OP.