It's a local institution. Marie Cat herself is well-known to locals and will regularly stroll…read morethrough the café to say hi to everyone.
This place specializes in crêpes (you are in Brittany after all), but also have a selection of other dishes that are pretty good as well - from grilled meat to fish dishes, to daily catch. The desserts - Kouigns - are pretty good, although not outstanding either. Beer selection is the same - very correct, but nothing outstanding.
Overall, I preferred the Tom café just across the road for the quality overall and also the price/quality ratio, but Marie Cat can also be a fun stop once, just because of how much of an institution it is.