It can be a very enjoyable production, with totally acceptable, if not outstanding food.
One thing I did not see mentioned in earlier answers is the length of the show: in order to prep, cook, and serve so many courses to a fairly large audience, and allow them time to eat everything, the show itself takes quite a while.
I have previously enjoyed several Cirque du Soleil shows in Vegas, with dinner before/after at a nearby restaurant. This was about the same overall length (3+ hours) of time, without the refreshing change of venue/chance to stretch the legs.
I noticed towards the end that several in my party were seriously flagging – a full meal with a couple alcoholic drinks, plus the visual overload really did them in. So, from that perspective, I'd say it's a great cuddly-comfort-building date for a semi-established couple – Valentine's Day springs to mind… But probably not an ideal first date (the show is not so engaging that you can avoid talking with your date if things aren't going well).
That the other answers seem to mention "company parties" makes a lot of sense – single venue is highly desirable, and Teatro basically runs the whole show, so there wouldn't be much planning involved. Along similar lines, the tables closest to the center always seem to be filled with birthdays and anniversaries… So perhaps the optimal attendees are groups, where the organizers don't have the skill/time/energy to plan out an alternative.
Is Teatro ZinZanni (San Francisco) a good place for a twentysomething date?