Aside from B/C which hasn't been in the full size console for a while now. The slim is an improvement. Reduced size, reduced power, etc.
Reduced power is an improvement..reduced size is debatable. End result is it looks terrible now. Now we have to wait and see if the reduced size doesn't cause the ps3 to start having 360 like issues. I am like a few people in this thread in that my PS3 is a serious part of my Media setup. Having my components adhere to a certain look and feel is pretty important. The original PS3 with it's gloss black and chrome, matches a good bit of AV equipment out there. The Slim with the matte finish does not. While the slim is fine if it were only for gaming, I am afraid this is no longer 1999 and Sony isn't marketing it as only a gaming machine. That makes this change a failure.