I really like certain aspects of the A900's controls and control layout, like the metering switch, two large, programmable custom function buttons, and the image stabilizer switch. I do have a tendency to confuse the stabilizer switch with the off/on switch when I'm in a rush, though.
If you're used to using a top status LCD, you'll find the A900's somewhat disorienting. It's tiny, and while shooting displays only shutter speed, aperture, shots remaining and a battery icon. You can also use it when setting exposure compensation, white balance, ISO sensitivity and drive mode, but it's easier to see the options on the back display.
The A900 has a nice, deep grip with indentations for all your fingers. It's necessary, though, because this is one heavy camera--the body alone weighs over 2 pounds, which is a lot for a camera without a built-in vertical grip.
Whatever you think about the body design, Sony does a very nice job with its accessories. The vertical grip, for example, replicates all the controls of the horizontal grip, most of which are in the same relative position, making the transition between vertical and horizontal shooting very smooth. In addition, the actual grip, shutter and front dial sit about three-quarters of the way down the grip, so can rotate the camera with the viewfinder remaining place relative to your eye.
Sony's cleverly design flash rotates freely 180 degrees horizontally; unlike traditional flashes, this allows you to shoot portrait and landscape with the flash remaining in the same orientation. However, you can't rotate the head around the Y axis the way you can with a traditional flash, which eliminates some of my favorite bounce positioning.