Sony a900 compared to the a700

I think you have received good opinions (pro and con).  A couple of things additional:

1.  Many of the mid price range Minolta lenses had issues with corner vignetting.  For example my 24-105 and 28-135.  The 28-135 could not even use a normal lens hood because of vignetting.  But with my APS-C cameras the vignetted area is automatically cropped away.  Yes, you lose the wide angle FOV, but going from APS-C to FF that has to be a consideration.  I saw that you did not have any of the mid-range zooms, but I don't know if the wide angle primes also had that problem.

2.  The firmware 2 for the A850/A900 significantly improved AF lock on and tracking which is an issue with my A700, at least compared with my Maxxum 7 film camera. (Probably the same space aliens who built the pyramids and the Nazca lines designed the Maxxum 7 AF, but they all left for home, and 21st century man can't figure out how to do it.)

3.  A big down side of the A900 for me is the lack of a built in flash.  For vacation photos of my kids I like to add a bit of fill on a sunny day with the pop-up flash, not carry around another flash that sticks up on top of the camera.  I also use wireless flash a lot (using my 5600 and 3600 together as remotes, and again don't want to have to buy/carry around another flash as a controller.

4.  The biggest downside of the A900 is its size and weight.  It weighs 50% more than my Maxxum 7 which was the ideal weight for me for long days hiking in hot weather.  But many people found that camera too light.

Even with my issues above, I would probably jump at the chance to get an A900 for $500, depending on condition.  I wouldn't sell my A700 however, since I see uses for both.

tom