Hmm, honestly ... I would suggest you skip it unless you can get some really great prices on Minolta lenses, and the A57 is cheap.
I have an investment into Sony/Minolta ... they make some really good stuff but it ain't for the low budget photographer. The only reason I have it is due to the legacy Minolta equipment that we had from the film days.
Honestly, there is soooooo much Canon/Nikon equipment out there that I would consider it the cheap way to go.
If you got money to spent ... then you would not be looking at an A57 ... more like an A77m2, the A99m2, or an A7something.