I just started a 14 day evaluation: T-Mobile w/Blackberry 7105t vs Verizon w/Treo 650. Synchronization with my ACT! 6.0 contact database is one of the main things I'm looking at.

After reading a few less-than-glowing comments about T-Mobile support I was a little apprehensive when the sync kept bombing out every time at contact record 444. My ACT database has ~4,500 records.

I'm happy to say that my T-Mobile support experience was actually quite good.

I'd already covered the basics on my own using the online help (from T-Mobile, Blackberry AND Intellisync). In my experience, doing this usually makes it better when I actually end up calling a human being on the phone.

I first spoke to Louise - very pleasant lady - at T-Mobile who went through the standard "tier 1 checklist". Once completed, she readily acknowledged that it sounded like something outside the normal scope of T-Mobile's frontline support. She put me on hold - maybe 1-2 min? - and got a tech "Alex" from Blackberry (RIM) on the line. We reviewed the steps I'd already taken, did some basic process-of-elimination troubleshooting, and got to the solution fairly quickly, which was this: Disable the NOTES synchronization.

Turns out the Blackberry has a finite amount of memory allocated for "Notes" and when you hit that limit, that's it.

It's kind of a bummer not having ANY Notes or History records so I suggested that in future versions they may want to taking the approach Palm uses: When configuring the sync, you can specify to xfer the most recent "N" Notes and most recent "N" History records.

Hope this info is helpful...

See More: Sync Problem (and solution!): Blackberry 7105t & ACT!