I sometimes really wish more Newfoundlanders bothered with review sites and the internet etc. We really don't.
There are a LOT of hidden gems in Newfoundland, and in St. John's in particular that get overlooked constantly. There are several places in St. John's that serve excellent food that I haven't seen mentioned anywhere. The only places that seem to get mentioned are places that are new, recent openings. Those types of places are hit and miss anywhere in the world.
If depends on what you consider good food as well. Since you liked the scrunchions and bread pudding, there are definitely a LOT more places that you haven't been that have great food.
Now I'll be the first to admit that Newfoundland isn't exactly the picture of fine dining, but people coming in that do these sorts of reviews seem to expect that, I have no idea why. Do I expect to find a load of pan fried cod and scrunchions waiting for me in Montreal? No.
Newfoundlander's who would be the restaurants main customers, tend to prefer their food to be salty, and somewhat heavy. Most everything is fried(pan or deep) or boiled in Newfoundland. The oven is for bread and pies.
Roasts/Chickens in a roaster would be the main exception to that, but most Newfoundlanders I know prefer stew anyways. Which is best done in a cast iron pot on the stove top, but often done in a roaster in the oven.
Most of what I'll call regular folks, come to Newfoundland and leave 10lbs heavier. There is a very good reason for that, and it has nothing to do with the light salads and vinaigrette sauces etc that a lot of reviewers seem to think are necessary for side dishes and appetizers. There are a few restaurants in Newfoundland that attempt to cater to those types of folks, but they're not my cup of tea.
That said, I have a few St. John's area locales for you.
By the Beach in St. Phillips/Portugal cove if you haven't been there is absolutely fantastic. I highly recommend the pea soup and toutans personally.
If you're in the mood for fried fish, Scampers Fish and Chips on O'Leary Avenue near Avalon Software is great for a quick bite. I recommend the deep fried scallops. Sometimes the food isn't so great there but for the most part its leagues ahead of Ches's fish and chips. If the decor is a bit worn.
We have a running joke back home that Ches's stays in business by advertising and tourists, and no one wanting to admit they got duped so badly. In regards to usual Newfoundland food they over-bread their fish and 90% of the time the cooks seem to have forgotten where the salt shaker is.
Admittedly it may taste better to an outsider, as we tend to prefer things saltier on the Island, however I've heard some outsiders complain that Ches's is too greasy and extra salt like you get in most other Newfoundland restaurants would actually help to cut the grease a lot.
Other than that there are some great Chinese food restaurants around town. The China House in the Torbay Rd. strip mall is a bit of a hidden style hole in the wall establishment that generally has really good food. Fresh veggies, fresh meat, and a cook that really knows what he's doing in the kitchen. Its also quite nice once you get inside.
I also enjoy the Red Pepper's stir fry "create your own" all you can eat style restaurant as well, however this might not be for everyone. Most people I know either love it or hate it.
Then if you head up into Gros Morne National Park theres Jackie's out in Rocky harbour. Their food is usually fantastic.
The Deer Lake Hotel has recently acquired a new Manager(my cousin, actually) and let me tell you, this man knows his food. The place is already developing a good reputation.
Then also in Deer Lake and out in Goobies,and well pretty much wherever you can find one, are the Irving Big Stop Restaurants. They're usually staffed by good local Newfoundland cooks and are always a good stop for a nice hearty good tasting meal. I pretty much stop at every one I pass.
There is also a red sided Chinese food places who's name I can't remember for the life of me along the highway in Badger, pretty good food. It's a good place to stop if you happen to be driving across the island and come across it around mealtime.
Hope some of that helps :)