Smartphones are widely available and Windows Mobile based smartphones are plentiful. But there aren't many smartphones, Windows Mobile based or not, which can accommodate two SIMs. That is the great lure of Acer's DX900. You can put two SIMs into it, from different or the same operators as you choose, and switch between them freely.

Now, the lure of this idea is immediate. Anyone who has a phone for work and another for leisure might be drawn to the concept. It works well, too, thanks to the software Acer includes to let you manage and use both SIMs.

There is, for example, a SIM manager that lets you edit contacts on either SIM. When sending SMS messages it is a breeze to choose which SIM they should go from. You go through the usual SMS creation screen and then, at the end of the process, decide which SIM you want to send from.

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It is similarly easy to switch when making voice calls, and even the home screen delivers signal strength details for both SIMs at the same time.

This feature aside, the DX900 is a fairly straightforward Window Mobile Professional device. It is a 3G device with HSDPA and has both Wi-Fi and Bluetooth for wireless connectivity. There is a GPS antenna, a front camera for two-way video calls, and a 3.0-megapixel main camera with LED flash and self portrait mirror. The DX900 even supports TV-Out, though sadly it doesn't come with the cables you need to make use of this feature.

Like the best of today's smartphones there is a gravity sensor so that the screen switches orientation as you twist the phone in your hand. There are some neat software extras such as Namecard Mobile which works alongside the camera to scan business cards straight into the contacts software.

The device is fairly large at 106mm tall, 60.5mm wide and 17mm thick, and it weighs 147g. This is a little over the odds for a Windows Mobile device and we don't think that is solely due to the dual SIM support.

If you are a mobile music fan you may also be wary of the 2.5mm headset jack. You will need a converter to 3.5mm to use your favourite earphones, and the jack's location, on the left side of the hardware, means there will be quite a protrusion in your pocket if you do use an adaptor. This might mean the DX900 no longer fits into your favourite pocket, and/or that the headset adaptor snags the pocket.

The 2.8-inch screen delivers 480 x 640 pixels and it is a little under par when compared to others. It wasn't quite as touch-sensitive as we'd have liked, either. Battery life was about average for a Windows Mobile device: if you are a heavy user of hungry features like 3G, GPS or Wi-Fi, you will probably need to ensure the phone is topped up every day.

If you want dual SIM support in a Windows Mobile device your choices are limited, and this one is certainly worth considering. But if you are choosing a phone for other reasons there are slicker, sleeker options out there.