I have lived in the neighborhood across the street from Mario's for 8 years now, but just now getting around to writing a review. If you asked me 5 years ago about this place, I would have rated it 2 or 3 stars. However, I'm pretty sure they tweaked the recipe to their pizza, and it's now my favorite pizza in Charlotte.
Overall, I think the prices are fair, but I do think $1.75 per topping is a little steep. If you eat there, the complementary garlic knots make up for it a little. I would say 80% of the time, the garlic knots are cooked to perfection (warm and doughy), but the other 20% of the time, they have been luke warm and a little stale. They will swap them out for fresh knots if you ask nicely, however.
Not sure if anyone has seen that Family Guy episode where they poke fun of "Every Pizza Place" and how they ruin a salad, but Mario's is slightly guilty of this. The salad being put in a lasagna tray on top of a hot pizza box is not uncommon. I don't eat at Mario's for the salads, so no big deal for me.
My main recommendation would be to change around the draft beer selection every once in awhile. They've had the same draft beer for as long as I can remember. The only thing they seem to rotate is the Sam Adams seasonal. They keep the beer on the "John's Place" side, which is a bar owned by the same guy who own's Mario's. The cool thing is there is a small hallway connecting the two establishments, so you can always decide to go sit in a more adult friendly area (no kids allowed in John's Place).
One final kudos ... fantastic fried pickles and above average chicken wings.