Excellent excellent excellent!
I've been at least a dozen times, and Gurulukshmi is consistently good! I've taken a number of people, including my very picky mum and MIL, and both LOVE this place.
I usually get the Mysore Paper Dosa without the potato filling - it's huge, but easy to work through because it's all dosa and no filling. I've had the Chaat Dosa, Chole Dosa and Pav Bhaji Dosa and they're all good. For starters, get the Medu Wada. The chutneys that come with the dosas and most appetizers are amazing too!
The ambience is pretty decent and the bathrooms have always been clean (this can be hit or miss at some Indian restaurants in the GTA).
The wait staff is incredibly efficient, although the folks at the welcome desk aren't always on top of their game. Still, it works.
This place is HUGELY popular and always busy - I highly recommend you make a reservation regardless of the day and time you're going.