And another point (as I'm on a rant!)
A quick guide to data rates: Data rates are dependant on two things.

1. No of timeslots available (1 timeslot is used per voice call). GPRS can have up to 4 down, 3 up.
2. Amount of data error protection.

The 170Kb 'claim' is for 4 slots, unprotected data and this is true. My main point is this: this is not a real life rate and these claims were really backed off in 2000 as real data rates were seen on GPRS deployments I would be suprised to see these sorts of numbers in official marketing. In reality two timeslots, with moderate data protection will probably get you 35-40kb. This is still a lot better than a GSM data link of 9.6Kb (max) real life dropped packets brought this down further. (Hence the fiasco of GSM WAP but that's another story)

On the other hand phones capable of more timeslots are coming onto the market and the network software allowing for reduced protection coding schemes are providing faster data rates in areas with good signals. So slowly GPRS is evolving and getting faster, closer to the 'holy grail' of 170Kb.

P.S When I refer to protected/unprotected this is datastream error protection, not encryption which is a default of GSM networks (which GPRS uses).