A recent study by AirCom of Vodafone and Orange 3G networks has shown that indoor, contended download rates typically average 198kbps and 178kbps respectively. This is significantly less than the advertised maximum speed of 384kbps.
Orange and Vodafone have both stated that HSDPA trials will begin at the beginning of next year. HSDPA, sometimes called 3.5G, will provide up to 1.8Mbps but it is expected that users will initially experience more like 425Kbps.
Prototype handsets are already available. T-Mobile has also announced that it will sell a HSDPA product next year providing up to four times the speed of 3G.
Speed isn’t everything. Latency, the measure of the time for data to travel from the phone to the server, is a larger issue. For example, VOIP is unusable on current 3G networks, not due to the speed, but due to the typically high (250ms or more) latency. The time for data to go from user to user is too long and the conversation is delayed. HSDPA should reduce latency to about 120ms and make applications such as VOIP more feasible.
For further reading, Nokia has video and white paper describing HSDPA.