First, we should explore whether mobile broadband is in any way equivalent to its fixed broadband equivalent. The term "broadband" can refer to any speed over and above 256kbps, or 0.25Mbps. So in the UK, broadband can mean anything from BT's recently discontinued dual-ISDN lines, right up to 24Mbps ADSL+2 connections – a huge sweep of services, all coming under the same banner.

Of course, mobile networks are obliged to advertise the speed of their broadband services – but here we enter even murkier waters. Michael Phillips, product director at Broadband Choice, while acknowledging that these dongles perform "reasonably impressively", is not entirely happy with the claims made by the networks.

"We have a real problem in this country with the way that broadband speeds are advertised," he says. "You would have thought that the networks would have learnt from the problems faced by the fixed line companies, and be more realistic." (Indeed, BT called for action from OFCOM on the issue of net speeds earlier this morning; even if you ignore the common misconception that an 4Mb connection will somehow deliver you 4 megabytes per second, there's still a great deal of deception out there.)

Three of the four companies advertise 3.6Mb connections, while Vodafone – implementing a slightly different system – are offering a maximum speed of 7.2Mb. I don't own any of the dongles to perform a real-world test, but Michael Phillips, again, is at pains to point out that you're unlikely to see the same performance as from a fixed line.

What he's more concerned about, however, are the data limits within the contracts, and the punitive charges should you exceed them. Many of them offer a 3Gb monthly limit; until recently, that would be sufficient for most people's needs. But with the huge take-up of services such as the BBC iPlayer, it's pushing people's data transfers through the roof; suddenly, your mum and dad could be termed heavy users, and penalised if they're not on a plan that suits them. Currently, mobile broadband doesn't offer any such plans.

But the service is still incredibly useful for two sets of people: firstly businessmen on the move who, up until now, have largely connected to the internet via Bluetooth on their mobile phone (not particularly speedy, and often breaking the terms of their mobile contract), and then groups such as students and visitors from overseas who might not stay in one residence for long; until recently, their options were limited to taking 1-month fixed-line broadband contracts – and interest in these has seen a marked dip in recent weeks, according to Broadband Choice.

Of course, as speeds increase, mobile broadband will eventually pose a real threat to fixed line model. Right now, however, the only people who should be worried are the providers of Wi-Fi hotspots, which are surely staring extinction in the face. Indeed, one commentator this week described the hotspot as the "telephone booth of the broadband era".

CONFUSED ABOUT TECHNOLOGY? SUBMIT YOUR QUERIES TO CYBERCLINIC USING THE COMMENT FORM BELOW, OR EMAIL QUESTIONS HERE.