Tamarind has an amazing menu, with both North and South Indian dishes (the only place I've found in Pittsburgh proper that does both). I have been several times, and I'm continually impressed. It is a bit more expensive than some of the other Indian restaurants close by, but so worth it!
The dosas are delicious, and so are their curries. An Indian friend considered it the most authentic Indian place in Pittsburgh. Like most Indian restaurants, they also have a great vegetarian selection; even non-vegetarians should consider branching out and trying a dish sometime.
It's a great place for a date, but serves well for large groups and friends. They also have meal specials on Tuesdays or Wednesdays for students (I can't remember the exact day).