I consider Osmow's as my second best shawarma restaurant in the GTA based on my last experience (#1 best is Lazeez, obviously). The reason for my rating of 3 stars is because of the inconsistency i've experienced.
I have probably been to Osmow's Courtney park at least 5 to 6 times. The last time I went, the shawarma was warm and tasty and the service was friendly and not too slow.
But my previous visits have involved an extremely long wait, rude employees, and cold wraps despite them warming it up in the toaster. Also, their hot sauce spice level varies, as once I got the medium heat and it was extremely hot, while the other time I could barely taste any spice at all.
During my most recent experience there, i'm assuming the service was faster and friendlier since it wasn't too busy, and thereby they also made the food with more care.
So, in conclusion, I would recommend Osmow's when it isn't too crowded, during which the shawarma is more likely to be up to their potential.
An advice: keep in mind that their wraps tend to fall apart due to their heavy-hand with the sauces, especially the garlic sauce and they do not have plates. So ask for less sauce if you want to spare your clothes.