If you're still agonizing over which mid-range DSLR to purchase, perhaps ePHOTOzine's 2009 DSLR Group Review Report might help.
The article compares 5 DSLR bodies: Canon EOS 50D vs Nikon D300 vs Olympus E-30 vs Pentax K-7 vs Sony A700.
The A700 emerged as the overall winner, with the following verdict:
The Sony Alpha A700 wins because of the specification being so similar to the other models, it gives good noise performance, has great color rendition and a good dynamic range that seems to work even when dynamic range compensation is switched off.
A useful summary of pros and cons of each camera is given at the end of the review.
Paul Graber posted excerpts from the K-7 review (which was written by Angela Nicholson):
… she likes the camera quite a lot, finding it "extremely comfortable to hold and use". She likes IQ and detail resolution, and unique-to-Pentax features such as built-in level adjustment. Live View now fully rounded and of genuine use. During review process, she adds latest firmware and notes improvements. But she finds a few niggling problems:-
* AF improved, but still behind Nikon and Canon
* Viewfinder not that comfortable to use and a bit gloomy
* Menu system less flexible than competitors
Also, the Canon 50D and Nikon D300 / D300S might be preferred by sports photographers for the Autofocus speed, but "… landscape, still-life and macro photographers could well prefer K-7."
Pentax K10D vs Nikon D300 vs Nikon D90: High ISO Image Noise Performance – Jeff Kott:
I have a Pentax K10D and six limited lenses. I also have a D300 and recently bought a D90 to get similar image quality as the D300 in a more compact package.
I find in going back and forth between the K10D and the D300/D90, that I really appreciate the extra DR and lower noise of the Nikons especially at ISO 640 and 800 which I use a lot.
I make a lot of 16"x 24" prints and find that I can shoot with impunity at ISO 640 or 800 with the Nikons and get acceptable images with a little bit of noise reduction at ISO 1600.
When I print large with the K10D, I need to use noise reduction software even at ISO 400.
Canon T1i / 500D vs Nikon D5000 vs Nikon D300 – Ken Rockwell:
If you demand more pixels and count every one, the Nikon D5000 (or equivalent D90 or D300) gives superior technical results from their lack of noise-reduction induced smudging, ability to correct lens defect color fringes and more reliable AF system. If you look at your photos at 100% on-screen, the Rebel T1i images look more like they came from a compact than an SLR.
Autofocus performance on the Tamron 17-50mm? – Udo:
I bought this lens about two years ago. I am totally happy with it. It is much better than the 18-70 it replaced, which is no slouch either. The Tamron stays on my D300 for about 90% of all shots. The focussing is louder than most other lenses, as already mentioned, but it does not bother me either. What is more important to me is that I never had a single missed focus lock in the two years I used this lens.
Tamron 28-300mm VC on the Nikon D700? – dbl00buk:
Very surprised at the results on my D700.
I must have a very good copy because it actually has better stabilization than my 18-200mm VR on my D300 all the way out to 200mm. Sure, the Tammy sounds like a Maytag washer when the VC is engaged but the hold/stable effect is amazing. I've been getting great sharp, color images.