After having lived in Mysore/Bangalore for 10 years, I know a great dosa when I taste one. We have tried tons of places in the GTA which 'claim' to be authentic, but Guru Lukshmi is the real deal. Starting from the sambhar to the chutneys to the dosas, these are the tastes you can find in Karnataka/Tamil Nadu.
I agree, the prices are steep, but it is a treat to go once in awhile. Their medu vadas are delicious, so crispy and light. I always get the Mysore dosa, very flavorful, just like they make them in Mysore. Their Rawa dosa and other specialty dosas are just as good too. Their filter coffee is excellent and a great way to end a meal.
This location and the decor/seating beats the one they had earlier, which was dingy and cramped, but nonetheless, we still used to visit it simply because of the food.
I've always found the staff to be friendly and helpful and yes, even though the place is extremely crowded, but once you get seated, you are good to go. I never felt rushed.
It is better to visit during the weekdays before 7 pm.