I got the Orange SPV M2000 (same as O2 XDA II). I use it mainly with my TomTom GPS software and bluetooth receiver. It also has WiFi which is annoying to configure but a nice feature nonetheless. You can also put a sim card in it and make phone calls from it. Some people might call the slide-out backlit qwerty keyboard a nice feature, but I personally think its unnecessary and just adds to the width of the device.
Best of all, got it for £100 with a phone contract 18 months ago.