The Stratford restaurant scene benefits greatly from having a diverse customer base from locals to theatergoers and from the local cooking school. You can find top-notch destination restaurants like Rundles or the Old Prune, or far lower-priced but also very good places like Boomers Fries as well as many excellent mid-priced entries (e.g. Fellini's, the Annex, and several others). Mercer Hall fills a gap of sorts, being fancier than the middle group, but not as much a destination restaurant (with associated prices) as the top group.
Mercer Hall is in the former Tango space on Ontario Street. I say that, but apart from the street address it does not even remotely resemble the former tenant. Tango was deliberately bright, casual, and colorful; Mercer Hall is elegantly decorated with wood floors and cool, sophisticated colors.
Our service was attentive and efficient. We arrived at 6:00 and they immediately asked whether we had a show (which we did) and our appetizers, entrees, etc. all arrived relatively quickly. We were able to finish in plenty of time for our show without feeling rushed. There were others around us without theater plans and the service was paced accordingly.
Mercer Hall boasts organic and locally grown food and the offerings reflect culinary flair. You might want to look at the menu online ahead of time to see the types of food available. I thought the menu was a little short and would have preferred one or two lighter offerings. As it was, we had the trout and bison, both of which were delicious.
Mercer is on the high end of nice restaurants before seeing a show.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.