Unfortunately the problem with the Xperia X1 is not just the fact that the panels are weak, it's also that they're so slow to load. When you switch to a panel the phone first shows a static low resolution image of it before slowly morphing to the high resolution version that you can actually interact with. The average time for each panel to properly display is a full six seconds when the phone isn't doing much else - it can take a lot longer when tasks are running in the background.
The only really useful panel isn't even pre-loaded on the phone, instead you have to download it from the Xperia website and install it yourself. It's a reworking of the Spb Mobile Shell, which gives you access to most of the phone's features via a 3D grid of icons - it's almost identical to the interface used on O2's Xda Zest. While this panel isn't perfect it does actually make the handset much more useable as a touch device as with all the other pre-loaded panels you usually have to resort to the stylus at some point or other.
There are a couple of other niggles as well. Despite using a Qualcomm processor rated at 528MHz the handset has a tendency to feel a bit sluggish. Sometimes applications seem to freeze up for a while as it sorts itself out and switching between programs can also be slow.
We're also not overly keen on the phone's D-pad control. The centre of the D-pad operates as an optical controller much like the one on HP's iPAQ Voice Messenger, but although it's useful for scrolling through long lists, such as all the entries in a your contacts book, it's not very accurate and it also tends to activate itself when you're simply trying to click up or down with the outer clickable part of the D-pad. Luckily, however, you can disable the scrolling function in selected applications or turn it off completely.
We had expected great things from the Xperia X1. In terms of the hardware it certainly lives up to the hype as it's a great looking phone and packed full of useful features. However, the hardware is really hamstrung by the phone's operating system and the X Panel interface that Sony Ericsson has added is over the top. At the end of the day when you pay a premium price (this is an expensive handset after all) you expect premium performance and the Xperia simply doesn't deliver that premium experience on the software side.