It seems that is work for most users with rom based on DRC83. It seems that works in US and EU region. Therefore I decided to start separate thread (something was discussed in cyanogen's thread).
I tested it on cyanogen 18.104.22.168 but it should work with other ROMs too. I think that improvement is depedent on presence of HSUPA feature in your network.
Try it and let us to know....
Comparison video - two G1 simultaneously (sorry for poor quality-Nokia)
I have found that my cyan G1 is much slower in uplink in 3G network than official TMO EU G1. Same radio but "primary band" (phone info menu) was different....
Cyan (and other US ROMS):
I found difference in build.trout.prop (build.prop - TMO) which make this difference.
Cyan (TMO US):
I changed values in build.trout.prop.... TADAAA
62.50S.20.17U_22.214.171.124l is showed in phone info. Uplink is almost three times faster. It seems that is some improvement in EDGE too (gprsclass).
US ROMS has disabled HSUPA feature.
ro.ril.hsxpa=0 - UMTS r99
ro.ril.hsxpa=1 - HSDPA
ro.ril.hsxpa=2 - HSDPA/HSUPA
script which apply all stuff (thanks cloverdale)
note: script use cyanogen build.trout.prop
1) adb pull /system/build.trout.prop build.trout.prop
2) edit with notepad++ (or other unix format capable editor)
3) adb remount
4) adb push build.trout.prop /system/build.trout.prop
in on other roms change build.trout.prop to build.sapphire.prop or build.prop depending which one your ROM using