Hi Tom,
I use the contax 645 with a P45. Before I got the P45 phase gave me the P25, which I had for about 5 months before the P45 was shipped to me. This is three and a half years ago.
I was absolutely blown away at the time at the detail, and the beauty of the P25 files. The step up to the P45 after that was nice, but basically the feel of the files was very similar.
I shoot several thousands of products a month tethered in the studio, as well as various shoots on location, shooting people. The closest to landscape I guess would be architecture work I do. At least, that's when I put the contax on a tripod and shoot at high f stops with longer exposures. In all these situations I've been very happy with the system.
I'm definitely one of those contax 645 users who's attached to the system, and I love the lenses and the feel of the system, and so am biased. I never used it with film. I switched to the contax when I had to decide on a medium format digital workflow.
It's quite a beautiful camera. It feels really great in the hand. I think for the money you'll be more than happy.
I put the nikon eyepiece on a couple of months ago, and I'm not convinced. It feels just a little bit more fuzzy than without. But, I've been too lazy to take it off agin, so I guess it's alright, but I think the idea sounds better than the reality. It didn't make a siginificant difference. In fact I would say I was a little disappointed.
I have the 35mm, the 45, and the 55 for wide angle. The 35 is a must. I took ages trying to find the 55, bought the 45 at the same time, because it was going cheap. In the end I've ended up using the 45 a lot more than the 55. The half stop more light may be the reason. But, also it's just a really nice lens. Wide, but not so wide that you can't shoot people with it.
The 80mm is my workhorse and is just such an amazing lens that I couldn't use enough superlatives. What's specific about this lens to me seems to be that it's incredibly sharp at it's sweet spot, but does really beautiful things in the not so sharp areas. I'm not just talking about the boket, I mean where other lenses are still sharp, the 80mm for the contax is just ever so blurred in some areas. I put this down to modern MFDB lenses being precision made for the digital backs, while this lens was made for film, and probably isn't so perfect, as such, but has an awful lot of character. Perhaps sounds like bullshit, but it's how I feel it. And the 80mm with my contax is the main reason I'm so attached to the system.
I also have the 210mm, which is very, very sharp, but I hardly ever use it. It's heavy to lug around.
I would definitely recommend the battery pack. It makes the camera easier to hold. I use the battery pack exclusively, and never the CR2s. But, that's me not wanting to spend a lot of money a month on batteries. I have a rolling system of 5 sets of 4 AA batteries which I have charging all the time. I've found that the CR2s last less than the charged AAs, and remember thinking that they were bloody expensive, considering I needed 2 or 3 a shoot.
In moments of sobriety, and thinking about a professional system that would perhaps suit my needs better, I feel that an integrated MFDB and camera which would use just one battery would be an advantage. And my contax and P45 is pretty sluggish. When I shoot people, then I sense the need for more speed. I never use the autofocus, unless I'm holding something in my left hand.
Good luck with it
Stefan