Initially I was handed the camera with both grips. Now I like grips, and I liked this one a lot. The camera felt instantly very comfortable, both in horizontal and vertical positions. It also felt comfortable without the battery holder portion of the grip as well. Without either, its actually quite small and essentally much like any other CSC.
As I said, I like the feel of a camera with a grip, and feel the handling is often much improved. The advantage with the OM-D is that its still pretty light with it attached. The two grip sections are actually quite small and add little weight. There is some extra weight obviously from the battery. The whole thing in the hand is not unlike cameras like the Nikon FM2 and Pentax MZ-5, which is no higher complement in my book.
Olympus seem keen not to class this as "professional" m4/3 but it essence thats exactly what it feels like. Finally someone has produced a digital camera that looks (its VERY classy) like a professional tool without the ridiculous weight and bulk that some modern DSLR's can have.
Taking pictures with it you become aware af several things. The rear screen and viewfinder are really good, sharp and clear. The AF is just lightning and THERE IS NO SHUTTER LAG!!! I pressed the shutter down and it felt that by the time I'd got the shutter down all the way it had already taken 4 pictures! Absolutely astonishing and completely different from any other m4/3 cameras. It doesn't seem to struggle in low light with low contrast and was one of the fastest cameras I've ever handled.
Using it, I wanted one very badly. However, at this current time its not a camera I have a lot of use for. Olympus were offering a show only deal, which meant if you pre ordered it there you got the grips plus case plus extra battery and a couple of other things thrown in. I even managed to resist that.
As you can tell I was very impressed. If at some point I ever go back to shooting weddings, portraits, events etc. I will buy one like a shot. Many of the samples circulating that I have seen indicate that this sensor and processing engine has improved high ISO performance and dynamic range, and combined with the modular design, superb (there's no other word for it) handling and sheer speed this is a camera that I would really enjoy using and that should be a real alternative to cameras like the Nikon D7000 and Canon 7D.
THE FUJI X PRO 1
UPDATE - 8/3/2012
Just to say that I don't seem to be completely alone in my assessment of the X-Pro 1!!