I don’t think the answers so far do full justice to MFNR and A99 owners may be discouraged from trying it. In my experience with the A77, results are much better than one might anticipate. It can deliver acceptable JPEGs in circumstances where other options may be impractical; museums and interiors where flash and tripods are prohibited are prime examples. Also, the subject need not necessarily be completely stationary. I have obtained decent results where the subject is quite definitely moving. For example see the night-time shot below – taken through a store window with the subject rotating at about 2 rpm. This was taken in ‘Hand-Held Twilight’ Scene mode, which has limited user-set shooting options; no editing has been applied.
Additionally the A77, like the A99, offers MFNR under ISO settings. That is still limited to JPEGs but the user has the ability to vary shooting conditions, such as selecting a specific ISO value or focus point.