Since the X31 is based on Intel's Centrino standard there's an 802.11b Wi-Fi adapter inside. In use the Wi-Fi worked flawlessly in all environments, although I found signal strength to be a bit of an issue in my home. This however isn't really a criticism of IBM as I live in a very old house with thick walls, and the X31 didn't drop the signal once even under this 'hostile' wireless environment. Unlike the T41 and T41p ThinkPads that I reviewed recently there's no integrated Bluetooth which is a shame in a machine that's likely to be with the user all the time. Bluetooth gives you the advantage of being able to get online via your mobile phone when you can't find a Wi-Fi hotspot.
The X31 is a reasonable performer considering it's size and configuration. The overall SYSmark 2002 result of 138 isn't the fastest score we've seen from a Centrino based notebook, but it's more than acceptable and will provide enough power for any applications that you're likely to want to run on a machine like this. Battery life was three hours and 38 minutes, which again isn't amazing for a Centrino machine, but considering the size and light weight of the X31 it's understandable if not completely acceptable. Obviously IBM is aware of the limited life of the standard battery and offers several options to enhance the power on the move. The most obvious option is the X30 series Extended Life Battery which will add around 0.5kg to the overall weight and some bulk to the underside of the chassis. The result is a pleasantly angled typing environment and obviously much longer battery life on the move. At a price of £164.50 the Extended Life Battery isn't cheap, but if you need to use the X31 for extended periods on the move it might be worth investing in.
Talking of optional extras, you're going to need to invest in the X3 Ultrabase. The Ultrabase is a port replicator that also features a media bay and space for another battery. Of course the most important aspect of the Ultrabase is the media bay where you can mount an optical drive, but this has to be purchased separately. So, if you want to use a DVD-ROM/CD-RW combo drive with your X31 you're going to have to purchase the Ultrabase at £175.08 and then buy the drive for an additional £233.83. You can of course get around this by just investing in an external USB optical drive, the cost of which will be much easier to swallow.
Ultimately this is where the X31 stumbles a little. With a street price of £1,213.07 the additional cost of the Ultrabase and optical drive will push the overall price up so much that I’d be tempted to go for a T41 (although unfortunately not a T41p) instead. Given, the X31 is slimmer than the T41 and if you don’t need to have an optical drive with you very often it will be a joy to carry around, but for me I’d suffer the slightly heavier and bulkier chassis of the T41 considering the cost differential would be negligible.
All that said, if you want a very small and slim notebook that you can carry around with you everywhere the X31 makes a good case for itself.
There’s a lot that I like about the X31 and given that I rarely use an optical drive on the move I’d love to have one in my bag everyday, although given the choice I’d probably still go for a T41. But if you’re set on an ultra portable you’d be hard pushed to find a better model than this.