What speed can I get with GPRS vs. GSM dialed?

T-Mobile allows users to dial into an ISP through their Pocket PC Phone, as an alternative a GPRS data plan. You only need to have a standard GSM voice plan to do this, along with an ISP. There are many free ISPs out there, so you essentially can have unlimited free data on weekends and at night. What is the speed difference between this approach and GPRS?

I did some non-scientific speed tests using a T-Mobile Pocket PC Phone Edition and came to these conclusions:

GPRS - average 40Kbps
GSM dialed to ISP - average 7Kbps

For browsing PDA enabled sites, the dialed isn't so bad. If you are planning to hit any normal full screen enabled pages, it's very, very slow. Feel free to post your results as a reply.