A couple of days ago I went on a trek with my new camera, to a place where I have been many times before. Some photos can be seen here:
http://www.paulobizarro.com/tema.asp?id=45(top 7 photos only)
All photos were taken with the 16-35 L MKII lens, a lens I am very familiar with from shooting slides. I have to say that I am quite impressed with the camera's performance, and with the level of detail I am seeing in the photos. As a background, I have been a slide shooter for the past 20 years or so, always with the EOS system.
The 5D MKII is my first DSLR; so far, I was hanging to my trusty 1V, because full-frame was so expensive (and I think it still is...). Through the years, I have built up a fine collection of L lenses, so I waited until a camera like the 5D MKII (or the Alpha 900, or D700) came along, until this segment was more mature. What I really wanted was a 1 series camera, but that is just too expensive for me.
Comparing the 1V to the 5DMKII, it is obvious that the "feel" is different, but the overall impression is still quite good. The image quality for landscape work is really good, so I am a happy photographer. Will I miss my 1V and slides? Of course I will, but that is life, I will just move on.
So far, no problems with my camera; I just noticed a dust speck in 3 or 4 images, but that was gone in the following images, so that is fine. For years I had to spot clean my digitized slides, so if I have to do the same with the 5DMKII files, I am ok with that. Plus, I don't blast away like mad on the shutter release, so I do not end up with lots of images to process.
Overall, a very good experience so far.