People take excellent photos using Canon, Nikon, Sony, Pentax, Panasonic and Olympus.
As for the image stabilization system, it is extremely important for some people, but not as important for others... it all depends on you and what you are taking. For Sony, Pentax and Olympus, these system came build into the body, so you can use lens without the image stabilizing system (IS for Canon, VR for Nikon, OS for Sigma, VC for Tamron).
And A55 is an excellent camera - although as many would have stated, it would have some lost in light, but seriously do these lost in light really matters? It would for some photographers but it is a non-issues for others. So it all depends on your style and genre of photography.
And like I say in my previous post, all camera brand design and made good cameras. You would have to ask yourself what features you wanted most for your camera, then zoom in on the brands and models of camera that offer you tat feature, then go down to the shop and test out these cameras to see if you are comfortable with the cameras.
No use buying a camera so packed with features but all of them hidden and you need a genius to unlock them or with so many features but all of them perform averagely or below average... or getting a camera that look on paper that seemed like a gift from heaven, but in the end, you do not like the ergonomic, menus layout, weigh, whatever.