I've read that the theoretical max speed of GPRS transfers is 150k if all 8 channels are used. In reality, in the US we see top speeds around 50k, with 30 - 40k being more realistic in metro areas where GSM providers are biased toward providing more channels and bandwidth for voice over data when system usage is high.
Setting the baud rate higher won't work. 1) the cellular radio doesn't behave the same way a wired modem does. 2) GPRS radios use up to 8 channels simlutaneously, each running at 19.2k, to give you that max figure. Most providers don't have the cell tower bandwidth to let you use that many channels simultaneously, hence the lower 40k figure.
IE should load pages much faster than you are seeing, and you should be able to connect to the Net whenever you want. Are you in a major metro area where many users may be congesting cell towers? Have you contacted T-Mobile about your frequent lack of connectivity and slow speeds when you do connect. Their reps should open a trouble ticket to examine cell tower capacity in your area.
-------------------- Lisa Gade Editor in Chief, MobileTechReview
Might be a bit late to help you, but might help others. I found two great places that can help you get your PDA connected to the Internet. If you want to do it manually it might take some time. If you are up for it Geekzone has a good tutorial that helps you configure and share the internet by using your Bluetooth enabled desktop or notebook with internet access as an internet gateway for your iPAQ Pocket PC with Windows Mobile 2003: