I think I've been reading
I've had many a chuckle when running Galleon or some other Linux browser and seeing it pop up a well-imitated IE error page.
They don't. IIS by default uses error pages that look very much like IE's. Newer version of firefox and all versions of Chrome ignore them (I think it does a file size test)
You shouldn't use SIP over a data plan. The latency would kill the conversation.
You're right that 3G probably can't do it. The higher bandwidth comes with a tradeoff in latency, which is why the standard GSM (which has something like 14.4 kbps) is used for voice despite its weakness for any kind of data.
I don't know much about the data plan breakage, but T-mobile does allow unrestricted access on the dns port, so you may want to try setting up a vpn on your asterisk server on port 53.
When I see Linux software being sold in my local retailer, that's when I'll know Linux is being taken seriously as an all-purpose consumer desktop OS.
Been to fry's or microcenter lately? Hell, even best buy sells and advertises the nokia n810
1 Mole = 007 Secret Agents