Well, I'm way past 600 shots now - much closer to 6,000! And I've used the a900 in -24C all the way to +36C temperatures. (I just got back from Polynesia - very hot!).
For DSLR work, primarily wildlife, I'm a Canon convert so my comments tend to be based on my experience with the 1D series of cameras. (I use Mamiya/Phase for landscape work, so I deem myself pretty critical.)
What I like about the a900 - fabulous viewfinder, great menu structure, easy MLU and delay, two batteries with the vertical grip, lovely tonality and SSS works with all lenses. (I always wanted Canon to produce an IS macro lens!) And did I mention lovely tonality?
Things I don't like are quite minor - the SSS doesn't inspire the same confidence that you're steady as Canon's IS does, because you can't see it in action. But it does work. Also, the shutter sounds clunky because of the mirror's articulated design, I think. The a700 which I have as a back-up is much quieter.
My only serious gripe is that if you leave the camera turned on, hanging around your neck, you can inadvertently change some settings. Seems some buttons/joystick can be depressed by one's chest or maybe belt buckle. This is especially true if you're using the vertical grip. I leave it turned off now until I need it.
And finally - the lenses. My 24-70 Zeiss is way better at the short end than my 24-105 Canon was. The 70-300 G is fabulous as long as you can live with the smaller aperture. (Definitely better than my Canon 70-300 DO at the long end.) I like the 500 mirror lens but find I really need to use a tripod, despite SSS.
The 300 f2.8 and a 1.4X arrived just before my trip and I didn't take it with me so I'm just now trying it out. It's heavier - I think - than Canon's 300, but at first glance gives results that are comparable. It is eerily silent in operation. I'll check it out thoroughly in the next few days and report with pix....
And incidentally, much as I love Lightroom, ACR is a lousy converter for Sony files. Aperture seems best to me, but Capture One is very close and that's what I use for critical work because I use it for my Phase files, naturally.
An unabashed fan,
Bill