I think Pentax are doing the right thing with the K-7, it's small, highly specified and well-made. That and the maker's range of high-quality Limited glass is really going to appeal to a lot of people.
You simply don't get this with Canon or Nikon, their semi-pro models are hulking great things and rarely handle well with their mid-range primes. I'm thinking 35mm f/2, 28/24mm f/2.8, maybe 85mm f/1.8 too. Most of those lenses date back to the late 1980's and 90's and were designed for smaller 35mm models.
This isn't new territory for Pentax, think back to those excellent MX, ME and ME Super models from the 70's and early 80's. And don't forget the pro-level LX, there's quite a bit of that models DNA in the K-7. Of course it's a market that Olympus currently occupy with their excellent Evolt models, the E-30, E-620 and E-450 are the best we've seen from the company.
What's more it looks like Sony could be making more of a play for that segment. You may be too young to remember the word's first multi-mode SLR was the miniscule Minolta XD-11 (XD-7 in Europe), and I'm betting we'll see the A-700 replacement downsized this year too.
Rubber seals around the body and that of the battery pack provide weather proofing, but it looks like there's little protection around the occular (viewfinder). Maybe it's just the picture, we'll see.
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B&H Photo: Pentax K7 (body only)