...I guess it is also a way to play Sonic CD should my Sega CD ever decide to hate me.
Not really since it is based on the PC version. Don't take me wrong, for its time it is a great port but not Sega CD quality. The greatest port ever is Taxman's version on XBLA.
The best reason imo for getting Sonic Gems is Sonic Fighters and even that one is on XBLA these days.