I've been using the Droid Pro in the UK for the past 4 months with no problems. Battery life does suck, but the device is pretty powerful, and I usually keep WiFi on, so that's to be expected. I might pick up an extended battery over the summer, but we'll see.
On the T-Mobile network, the phone works great. I was with 3 for a couple of months, and it was downright horrible. I don't know whether it's a phone compatibility issue (shouldn't be, since the Pro works like any other GSM phone) or just their network, but I would not recommend 3 at all if you're looking for a network to use in the UK. The coverage sucks, the data speeds suck, and the customer service sucks. With T-Mobile, though, everything is fine. Voice is clear, data is quick, and phone works exactly as it should.
I've actually never used the Pro in the States, as I don't have Verizon back home, so I can't compare GSM vs. CDMA performance.