I can recommend the Desire Z, I've had some problems with it (syncing with the computer ruined my Outlook contacts list, and I've twice had all my text messages wiped), but I'm not entirely sure they were due to HTC's software, could be something all Android phones suffer from but it's just rare.
The keyboard is excellent! I thought it was too small at first (I came from an HTC Universal which is humongous and its keyboard is better than that of some netbooks!

), but I got used to the size. Travel and feedback are top-notch. The nonly thing that still bugs me is the lack of a separate numbers row. From the looks of the pictures it seems the Xperia Pro will also not have a numbers row, though the keys look a bit bigger there, and it has arrow keys, which should be a big improvement over the Desire Z (trust me, didn't think I'd miss them at first either, but they do make a difference!)
One thing though, I really don't think HTC have made any effort adapting the Android UI for keyboards. It's still centred around the touchscreen, and when you're trying to touch type having to move your hand away from the keyboard to tap something on the screen really slows you down. Some apps don't even let you move between different fields with Tab! And autocompletion is next to useless if you need to reach up to tap the option you want - it's almost always faster to just type to the end of the word!
You'd think that little capacitative touchpad HTC have put under the screen would help, but that thing is like a cruel joke. Its calibration is atrocious, its sensitivity completely borked (it'll either not detect your swipe, or it'll move more fields than you intended), and if you're trying to position a cursor while typing (which should've been the biggest use for it) its slow movement speed will make it faster to tap the touchscreen (again having to let go of the keyboard) and its imprecision will drive you nuts trying to find the exact spot you want, and you'll keep accidentally tapping it (which functions as a button that does different things in each app, for instance in text messages it sends).
That button functionality, in fact, is the ultimate design ****-up when they were making that touchpad. For one thing, it's a button. It's quite firm, but when pressed it has good long travel. You are in no doubt that you pushed that button when you want to do it. So great right? Wrong, cause HTC have decided to make it so tapping the touchpad has the same effect as pressing the button! And of course the damned thing is over-sensitive so detects taps when you never intended one, destroying any attempt to use the stupid touchpad to navigate anything! I mean, if you already spent the money to make it into a button why duplicate the functionality with something that makes it harder to use? And it's not just that the button press is screwed up - the software functions assigned to it make no sense either: when typing in the browser, say in the Google search box, and you get autocomplete suggestions, you can use the touchpad to scroll through them. Great right? Except pushing the button on the touchpad DOESN'T select the autocomplete suggestion you had highlighted! In the case of the Google search box, it'll just start the search instead. To select the suggestion you have highlighted, you have to instead move your thumb back down to the keyboard and press enter, which I think is an utterly moronic UI choice! (And you understand why I said I would've preferred arrow keys...)
So yeah, my point is, great phone, great keyboard, great hardware, but absolutely no thought given on adapting the software for keyboard operation! If you're not married to Android, you might want to check out how BB or WP7 work with a keyboard before upgrading. Hell, even Symbian would probably work better, Nokia's phones have been mostly keyboard-driven for years so I'm guessing that, terrible though Symbian's UI is compared to Android, it'll be better designed for navigating with a keyboard. The new E7 looks quite nice, and, critically, its keyboard has arrow keys!
