This is a great place for college/university students to congregate in. The place is really popular in Calgary; the patio is packed during warm, sunny days, and it's difficult to get a table in the late evenings.
Ironically, I didn't visit here much in my undergraduate days; I only really discovered it once I joined the working world when a friend took me to lunch and made me try the veggie burger (best in the city, he called it; he was right).
Many come for the live music or entertainment that happens often. For me, I usually use it to hold meetings with groups or colleagues, often getting a booth or staking out the tables in the back by the kitchen and dart board. The staff are very respectful of allowing patrons to take as much time as they need; it's a very casual atmosphere.
The food menu is very reasonable in terms of price. Many dishes are $10 or less, and the portion sizes are filling. My favourite item on the menu is the Ship Burger; made in-house and only $8 with fries.
If you're looking for some reasonably priced food options on 17th Ave, The Ship & Anchor is a great place to be.