Pho 88 is probably the most popular vietnamese food chain in Toronto. This location along with the Warden/Steeles location are the ones I frequent the most in the past 20+ years I've lived in Markham.
The pho here is excellent. The best in Markham by far. The soup is always tasty, the beef is thinly sliced and easy to eat, the noodles are always cooked perfect.
Last time I came to this Alton Tower location with my sister, we ordered a combo meal which was a great deal for $12 (two phos, two cold drinks, spring roll). I don't recall the name of the drinks (honey lemon ice tea?) but they were probably the best i've had at an Asian restaurant.
Definitely recommended for your pho fix! :-)