I don't think you'll find much in the vein of good/bad. It depends a lot on the source. If you play a full, richly separated stereo track, the surround effect will be good and effective. If you have a simple, almost-mono track, the surround will be minimal. Again, technically, in neither of these cases will the sound be 'ruined', with unexpected audio coming out from the rear speakers. It could happen, but it'd be an exception. The rule is for delicate, ambient sound added to the rear speakers. So, you will have to try for yourself and keep the effect if you like it, that's the ultimate test.
Since now all connections are digital, there's not to worry from multiple analogue-digital conversions as in the past. Of course, if you apply the effect to a device connected with analogue ports (e.g. a turntable), there's an extra conversion and the result might be slightly inferior.
You could try researching on Dolby ProLogic II to understand how it works. Before DPII, there was also DTS NEO: 6 - I didn't like it back then, haven't tested its newer versions.