I've have the Droid 3 for the past week and a half. I had the Droid Pro for seven months prior to that.
Yesterday, I returned the Droid 3 and went back to the Droid Pro.
The Droid 3 is a very good phone, but it's a little too buggy for what I need it to be right now. I, and many other users, experienced many problems - multiple random reboots a day, horrible battery life (even with the extended battery and all the knowledge of 6 years of smartphones - 2 years of Android phones - behind me for knowing how to tweak the settings and what to look out for), and a few other random issues. Also, their talk of an "improved" camera is hogwash. The pictures don't look any better than the X/X2 and only marginally better than the Pro in most situations.
Then there's also the form factor. I like phones with larger screens. I loved the Droid X that I had for six months. But I'm a physical keyboard person, so the Droid 3 seemed nearly perfect for me. The screen is a good size, and the keyboard is phenomenal. But it quickly became apparent to me that I liked the form factor of the Pro much better from a usability standpoint right now. This is just personal preference of course, and I would have gotten used to the Droid 3 (I had the original Droid and a Touch Pro 2 with landscape keyboards, so I wasn't inexperienced with them), but the Droid Pro just flows so much better for my everyday uses from a physical standpoint. Sure I'd like a bigger screen, but that's not the end of the world. That will probably change as my primary needs for the phone change, but right now from a business standpoint, the Pro meets my needs much better than the Droid 3. That point will be different for everyone, and I'm sure it will be different for me in the future.
The Droid 3 is extremely quick and responsive (although not all that much more than the Pro), and the new version of Blur is the least offensive yet, but there are still several issues that need to be ironed out. Motorola has acknowledged the reboots and battery drain issues on their support forums, so I'm sure a fix in the works. I liked the phone, and I really wanted to love it, but honestly at this point it didn't provide the significant leap forward from the Pro that I was hoping it would. Then add to that all of the problems I had, and I was wanting my Droid Pro back. I'd be willing to revisit the Droid 3 after most of the problems are worked out, but by then I'm sure there will be something new and better. For now I'm glad I went back to the Pro.
It's already a knockout 3G phone for those users who aren't experiencing any of the issues that are floating around, and there's no doubt in my mind that it will be the same for everyone once they address the problems that are floating around. But for me right now, the Droid Pro is the better choice.