yeah i was just about to answer my own question with a quote from John Clark
"The latest OS TMobile released is .64. The latest OS for all the Pearls was released by Cingular and it's .69. All OS's will work on all Pearls. They are all produced by RIM for any of the 8100's.
When you upgrade it will make a backup, wipe the phone completely, load the new OS and restore your backup so you won't lose anything.
The later OS releases are much more stable, fewer error messages and bugs. Also, support for 2GB media cards was added in later versions. The only downside of upgrading is losing the screen auto-dim disable feature.
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John Clark
T-Mobile 8100 w/Cingular OS 4.2.0.69 - BIS/BES 4.0 - Exchange
It doesn't get any better than the Pearl! "
thanks dudes