How fast is mobile broadband?

Firstly, it depends whether you have mobile broadband coverage (i.e. a 3G or 3.5G signal) in your area, so see our UK mobile broadband coverage page for links to coverage maps for Vodafone, T-Mobile and Orange. Even when you are in a 3G coverage area, as mobile broadband is a radio service, the service speed can vary greatly depending on local conditions, e.g. electrical interference. Note that the speeds quoted by service providers are usually "up to" theoretical maximums and the speed you can achieve in your area will usually be much lower. Vodafone currently quotes the fastest service speed at 7.2Mbps, and whilst under optimum conditions this would be as fast as most current home fixed-line broadband connections, and would be fast enough to stream online video, actual speeds obtained on Vodafone and other mobile broadband services are usually much lower (around 2 to 2.5 Mb/s). Online gaming places further demands on the broadband connection, see the fuller answer below.
When you are outside the 3G mobile broadband coverage, you will revert back to a GPRS-based service and this is very slowly, comparable to the speed of an old dial-up service or worse.
Note that when operating in a good 3G signal area using a mobile phone as a modem instead of a dedicated USB modem may reduce your maximum connection speed , especially if you are connecting the phone to the laptop via Bluetooth. However, when connecting in a GPRS-only area, the mobile phone is unlikely to be a limiting factor