I'm looking into switching from my T-Mobile Pearl and porting my number to AT&T and getting a Bold. Can I use the Switch Device Wizard the same even though I'm going between service providers. Should this cause any trouble for me?

Thanks,
Chris

Shouldn't cause problems. I have done this several times.

It won't cause any problems at all, and works pretty seamlessly.

As a precaution, always do a complete backup of your device first.
and

How do I backup my Third Party Applications on my BB? - BlackBerryFAQ