The device I’m using is a HTC Wizard, branded by Orange as a SPV M3000.
It runs Windows Mobile 5.0 with a custom ROM by Molski. The ROM is no longer for download on this website, but was based on a stable T-Mobile 2.26 ROM. I find that I have a clean ROM that runs without a lot of problems, so I can easily install a lot of software on top of it.
I really enjoy the slide-out QWERTY keyboard, so I think that if I get a new device, it will have to be one with a keyboard just like the Wizard (or it will need to have other killer features, that make me change my mind).
The bad things about the Wizard are the fact that the stylus is at the bottom and easily falls out, and the missing Start and OK/Close hardware buttons on top of the device. They are only available on the QWERTY keyboard. To work around this, I put SmartSKey on my device, and now I can long-press my left and right soft-keys in order to open my Start menu, or close an application.