I am not displeased with the a900 at all, far from it. And given the option of swapping what I have for a similar setup with a d700 I wouldn't do it, and not for the reasons of sticking with Sony and the communities.
I've been thinking about this a bit recently and personally I think the main issue is ACR and my workflow. I pretty much use LR exclusively, and output to TIFF (and then PS) if more advanced editing is required. 99% of my images come straight out of LR.
My only real issue with the a900 is the noise in the shadow areas, even at ISO200. Same photo, reasonable light, and 100% crop from the other side of the image.
Note that this image has had the exposure boosted by approx 2/3 of a stop (almost forgot, why does the a900 the majority of the time, underexpose?)
Not sure if I'm being very critical, but to me that looks like far too much noise to what I'd expect from ISO200 - but also the pattern is slightly blotchy. What this actually reminds me of, is the a700 images when it was first released.
I was trying to think back to what actually fixed this issue on the a700, whether it was just a gradual improvement in ACR for the a700, or whether it was updates to the a700 firmware. Doesn't seem that long ago, but I can't remember
Obviously you'd need to print huge to see this noise, which for me means it's really a non issue in real terms, since a bit of additional PP can clean this up.
I have seen images from DXO and the noise and grain does seem much better. But to change my workflow to include a pre RAW to Post Demosaic DNG with DXO, means more hassle/time PP, more expense, and more data.
To me, owning the a900 from early(ish) release just feels a bit dayjarvoo.