I'm the guy that posted the program up at XDA. Can't take credit for the porgram, found it at FreewarePPC.com
http://freewareppc.com/communication/tcptune.shtml.
The tweaks that I listed were based on trial and error testing for my sprint TP, re: the sprint network in my area. I have tweaked my PC's since, well forever, to increase internet speeds. Different networks react differently based on the tweaks you apply. The tweak settings that I listed work exceptionally well on sprint (literally tripled my speed).
The speed increases apply to all internet connections on your phone, browsers, downloads, uploads, and yes tethering. There is no exact science to tweaking your speeds. You have to play with the settings.
There are plenty of tips up at DSLRepots.com
http://www.dslreports.com/forums/all...o+speed+tweaks.
EVDO, and yes 1xRTT can both be tweaked.
I would love to see this thread take off with details of results based on what different tweaks have been applied, and what the results are.
Internet Speed tweaking has long been a practice on PC's but really has not been widely applied to phones with internet access.
Happy tweaking.