I enjoyed your quest for the perfect phone, because it parallels my own. I don't understand why the portrait QWERTY form factor doesn't get more love when you get out of Blackberryland.
Loved your commentary on the Blackberry, and I'm afraid I've stolen your phrase, "what the juddering fuck" for my own personal use. The whole BES thing generated much the same reaction in me, resulting in my ownership of a BB Torch lasting precisely two hours.
Anyway, I just wanted to say, if you've still got the Pro Plus it is worth giving it another go with the 2.3.6 upgrade. I upgraded mine immediately out of the box and it's been great - fast, fluid and reliable.
As an aside, I've also arrived here via a Dell Venue Pro. I loved the device and the keyboard was first rate, but I couldn't get on with WP7 at all. The real killer was having IE on my phone, and particularly its odd behaviour of making fonts randomly big and small across the same page. Not sure if that was a WP7 thing or a phone specific thinng.
Tl;Dr - give the Motorola another go. It's sorted me out and my use case seems very similiar to yours.