The DX900 is that all-too-rare thing – a dual-SIM handset. There's space for two separate SIMs under the battery, which can be very useful if you want to keep your business and private life separate, or prefer to have one account for voice and text, and another for data, but don't need the hassle of carrying an extra handset.
SIMs can be from the same, or different networks, or even from home or abroad, and you're given a choice with each call or text message to make it from the default Phone 1 or switch to phone 2, though it will automatically switch to the relevant SIM when you receive a call.
You can use different ring tones for each SIM and even disable one or both via the Communications Manager.
The Acer DX900 is very well connected, with HSDPA 3G fast internet connection (7.2Mbps) as well as quad-band GSM, Wi-Fi and Bluetooth 2.0 with stereo A2DP.
One point to note however is that although it can handle fastest-kind 7.2Mbps HSDPA 3G and quad-band GSM, it will only do so via the Phone 1 SIM connection
The Phone 2 SIM can only deliver GPRS/Edge and tri-band GSM. Not necessarily a deal breaker, especially if you really only want one SIM for calls, but it's a restriction that's worth considering, especially if you're more likely to use your network connections for data rather than the 802.11b/g Wi-Fi connection
Windows Media Player is the default music and video playing software, though this being a Windows Mobile device there are others to choose from.
Video displays reasonably well on the 65,000-colour screen but it's a shame you're stuck with the rather tinny and cheap supplied headphones thanks to the 2.5mm jack plug, unless you can get an adaptor.
Internet Explorer is the default browser and it's not bad, though you can download Opera for an immediate improvement in speed and functionality.
The zoom function works well enough though you'll need to access the onscreen menu to get to it and the onboard accelerometer, which includes a useful sensitivity setting, allow you to view web pages in landscape mode.