I'm a major Thai food lover, so I've tried lots of Thai restaurants in pretty much every city I've lived in or visited. Even by Toronto standards, Si Lom Thai Bistro was much more expensive than better Thai places I've tried (Khao San, Pai, etc), considering the portion size is also smaller. The Pad Thai tasted authentic and flavorful, but I would not come back here because it isn't worth the price you pay (I think I paid around $18 after tax for the pad thai).
Also a note for all you vegetarians out there - this place told me that they can't substitute tofu for meat in any of the curries or dishes. This basically leaves you with only 3-4 options from their "vegan menu," none of which include Thai curries. Every single other Thai place I've been to has been very open to substituting tofu for meat