If you've already read Sandra's review of the O2 XDA Exec, you'll notice that the SPV M5000 looks very familiar. To be honest the two devices are the same - at the hardware level anyway. One thing that you can usually be sure of is that four different network operators can use the same hardware but deliver different user experiences.
Let's get the obvious stuff out of the way first - the M5000 is a large device, not as large as my beloved Psion Series 5, but definitely large by today's PDA and smartphone standards. To be fair the length and width of the M5000 aren't any larger than most smartphone devices, but it is much thicker - 130 x 80 x 20mm (WxDxH).
The reason for the extra girth is the clamshell design - lifting the lid reveals a landscape aspect ratio screen and a full qwerty keyboard. Now, shoe horning a qwerty keyboard into a mobile device is one thing, but making it usable is something else completely.
Before you get excited let me make it clear that you won't be touch typing on this keyboard - you could try to balance the M5000 on your lap or a desk and type as normal, but you wouldn't get very far. This keyboard is designed to be used with your two thumbs while you cradle it in your palms - just like I'm using it right now in fact.
The design of this keyboard highlights the evolution of the human race. Over the past few years our thumbs have become far more dexterous than ever before. The use of mobile phone keypads and gaming controllers has resulted in our thumbs becoming the dominant digit on our hands. OK, if you're my age you probably still use your index finger more often, but if you have teenaged kids you'll probably find that they favour their thumb.
If you persevere you'll be able to type pretty well on the M5000, and you'll definitely be able to knock out emails with little or no fuss.