Another area that Sony Ericsson had tweaked on the X10 mini was the onscreen keyboard, using a custom T9 style affair rather than a QWERTY one. You still get this on the X10 mini pro, but with the addition of a physical keyboard you don't need to rely on it when typing long messages. What's more, not only is the keyboard a full size one, it's also very good.
It consists of four rows of ten keys, bar the bottom row with its enlarged spacebar. As such it doesn't have a dedicated row of number buttons, but in general use we didn't find this too much of a hassle. The bottom row of letter being shifted left to a while to become accustomed to, but again not to an outright annoying level. Moreover the small but pronounced keys are easy to locate by touch alone and the rest of the layout makes it doubly easy to concentrate on what you're writing, not how you're writing it. Ironically, we also found the narrow width of the keyboard made it easier to type, as compared with some larger phones with side sliding keyboards where we find them too wide to reach the central keys comfortably.
Normally we'd make the point that we can still type faster on onscreen keyboards, but given the X10 mini's screen size and the onscreen keyboard that it used, having a physical keyboard is arguably the only option for fast typing.
Another surprise of this phone is its battery life. While you'll certainly run it down quickly if you have lots of widgets and apps running, if you keep things sensible you should have no problems getting at least a couple of days out of each charge – not stellar, but impressive for such a small and capable phone. Call quality also threw up no obvious issues, though there's no active noise cancelling so it's not the best device for use in noisy environments.
Looking then at cost, the X10 mini pro comes in at around £250 SIM free (Next, of all places even has it for £199 at the moment), and free on monthly contracts of around £20 a month. This puts it firmly in the budget smartphone / premium feature phone sector in competition with handsets like the HTC Wildfire and LG Optimus GT540. As such it seems right on the money.
The Sony Ericsson X10 mini pro is a handset that requires many caveats before recommendation. If you're looking for a powerful and feature rich phone with as small a footprint as possible that has a physical keyboard then it is without equal. However, if you're simply looking for a good budget smartphone then there are other handsets we'd recommend.