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But we think that the biggest benefit of all is that you can forget about scrambling around trying to find a ludicrously over-priced Wi-Fi hotspot in train stations, hotels or airport lounges when you need to get on the web: the days of paying £8 just to check your email for ten minutes are well and truly over once you've got one of these dongles in your laptop bag. O2 cannily provides the best of both worlds, by giving its customers free access to The Cloud's 7,500 Wi-Fi hotspots when they're within range.

True broadband speeds?

While the convenience of broadband dongles can't be overstated, the connection speeds they're capable of achieving routinely are. Like ADSL, the advertised speeds are based on theoretical maximums that absolutely no-one ever achieves: real-world throughput is a mere fraction of what the networks claim.

Vodafone makes the boldest speed boasts, claiming downstream speeds of up to 7.2Mb/sec in its advertising, which isn't far short of the theoretical 8Mb/sec maximum speed of BT's ADSL Max lines. However, this speed is only currently available in select areas of central London. Six more cities are due to be added by the autumn, but even Vodafone admits on its website that those chosen areas benefit from "typical speeds of 1.7-5.5Mb/sec".

In our experience, you're likely to see true throughput speeds at the bottom end of that range. The fastest actual speed we achieved during tests was just shy of 2Mb/sec. While that's a long way short of Vodafone's headline figure, it's not far

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shy of the true speed that many people will get on ADSL - indeed, if you live more than a couple of miles from the local telephone exchange it might even be faster.

The other networks are way behind on claimed maximum speeds, although in actual measured throughput they can outperform Vodafone. 3, for example, advertises connections of up to 2.8Mb/sec on its "Turbo Network" (and we take our hats off to 3 for reigning in its marketing, as its service actually synchs at 3.6Mb/sec, which means it's advertising a far more realistic speed). And in our tests, we managed to achieve maximum throughput speeds of 2.6Mb/sec. Similarly, we managed to eke 2Mb/sec out of T-Mobile's 3.6Mb/sec network.

So why did the theoretically slower networks surpass Vodafone on speed? "Mobile Broadband is a bandwidth-sharing service," explained a spokesman for Huawei, which makes the modems for the majority of the networks. "If there are multi-subscribers in the cell, they need to share the bandwidth - therefore a single subscriber cannot achieve the theoretical 7.2Mb/sec download speed." Other factors, such as signal strength and electrical interference, can also affect connection speeds, so our figures should only be taken as a guide, not a definitive speed guarantee.

The other networks are far more reticent about their connection speeds. Both O2 and Orange claim a maximum speed of 1.8Mb/sec, although O2 was due to upgrade to 3.6Mb/sec just after we went to press. That's reflected in their actual-speed test scores, with Orange achieving a maximum of around 1Mb/sec and O2 reaching no higher than 440Kb/sec.

Yet, even on the modest speeds available on the slowest of networks, they're still fast enough for day-to-day web browsing and email access while on the road. And it's not only the mundane stuff they can cope with: all of the sticks we tested managed to comfortably stream video using the BBC iPlayer, for example. Don't bank on them for online gaming, however: with ping speeds in the hundreds rather than the tens of milliseconds, you could well find someone's blown your head off before you've even seen them on Call of Duty.