I had initially given up on 35mm film about a year ago, but I'm continually amazed at some of the images I get on such small film. Of course, there is always a major advantage to bigger film, but the advantage of a fast, lightweight system is obvious to me now, especially using such a compact rangefinder like the Nikon SP.
However, in an effort to possibly get a little more film real estate still with a hand-held system, I've decided to try a new camera. I used the Pentax 67 for a year and really liked it, but in the end it was very heavy, cumbersome, and didn't get me the image quality I was looking for. I wanted what I get from 4x5, which at the time I did not understand. But instead of the Pentax system, I am going to try out a Mamiya M645 Super. I found a great deal on one and am going to pick up the 80mm f/1.9 lens to compliment it and try some fast shooting with it. If I like it I might pick up a 45mm and a 200mm or something. The Mamiya system is really cheap right now for whatever reason so I was able to get the whole thing with a 110mm f/2.8 lens for under $300, quite a bit less than other medium format systems. I'm hoping with the smaller 6x4.5cm film area it will be smaller and have better film economy than the 6x7cm Pentax.
The biggest problem with medium format is digitizing images. Luckily, with an enlarger now I am less dependent on this, but for quality scans of this size film a scanner like the Nikon LS-8000 I had start at $1500 or so! It's easy to spend 4x as much for a scanner than the camera and lenses unfortunately.
Here are a couple of snaps I took while scouting a new area at Langdale Park (it is a really big place). I might have to take these on 4x5 sometime. They were taken on some old Ilford XP2 C-41 b&w film that I had around from last year: