I never got the ace, but i always wanted one. Had a friend that bought the ace to put it alongside his sb16. Like you said best of both worlds.
I got a Gravis Ultrasound ACE. This was a cheaper Ultrasound that worked along side an existing sound card. (Soundblaster 16 in my case). This was a win-win. It added the Gravis Wavetable synthesis which made game music sound a hell of a lot better than the OPL3 on the SB16, but still having the SB around meant 100% compatibility with everything (even though most things supported the Gravis). It was also designed to be daisychained, so it all played through a single pair of speakers.