Mill's Tavern is very high end and probably only for special occasions but I've never had a bad meal there.

Red Stripe on the East Side is a bit more reasonably priced and also excellent. We hosted an event there and all of our guests agreed the food was excellent.

Hemingway's is good for seafood, also somewhat high end. I think Red Stripe and Hemingway's might be a similar tier and Mill's Tavern somewhat more expensive.

We tend to go to Providence to eat as an event, so I'm not as up on mid-tier things because there are good choices for that outside of Providence. When I was in college, Angelo's on Federal Hill had good, inexpensive Italian options. A bit higher range on Federal Hill is Anduino's. Sienna is also very good and a bit more expensive, but not much more. If you were to go to Sienna, I'd recommend going in Smithfield because it is easier to park and the experience is the same.

I'd explore Thayer Street. The food scene in that neighborhood is always changing but Andrea's and Meeting Street Cafe are old stand-bys and relatively reasonably priced (The desserts at Meeting Street are killer). My Indian colleagues swore that Kabob and Curry was the most authentic Indian food in the area. I also like India on Hope Street.

Others mentioned Los Andes. They renovated recently and are quite nice inside. The portions are extraordinary for fairly reasonable prices and very tasty.