Even as pro-grade, mirrorless, interchangeable lens cameras threaten to overtake the user-base that once demanded budget DSLRs, not everyone is convinced. Sony has revamped one of its budget DSLR-like cameras for people who actually like having a bigger, more powerful camera in their hands.
The first thing you notice about the A57 when you compare it to last year's A55 is how much bigger it is. The camera's grip is larger, so the A57 will feel and carry more like a big-kid's DSLR than before. Technically, it's not a DSLR because it doesn't have an optical viewfinder, but for the purpose of better understanding the camera, it's very similar. It makes sense that Sony would try to distinguish the A57 from the excellent, compact Sony NEX cameras that have been released over the last year.
As for the camera's guts, the A57 has been upgraded to Sony's latest BIONZ processor, which enables the camera to shoot at full-resolution at slightly-higher ISO: Where the A55 went shot up to a standard ISO of 12,800, the new camera shoots up to 16,000. In the real world, you're looking at slightly better photos in low-light conditions. The A57's image sensor appears unchanged: it shoots with the same 16.1-megapixel APS-C CMOS sensor as the A55, and presumably, the same excellent sensor that's inside the compact Sony NEX-5N camera. As for other key specs, the A57 is capable of shooting at up to 12 fps continuous (impressive) and the camera, like its predecessor, shoots 1080p HD video.