I've dined at the Madras Cafe for several years. Maybe eight dinners and one lunch buffet. Most recently in July 2011. Vibrant dishes, fairly quick service.
I've been with a variety of friends, some very savvy, some newcomers to this cuisine. Reactions have ranged from very pleased/surprised to ecstatic, mostly the latter.
Service is pleasant, and very responsive. Decor is simple. Lightly remodeled a year or so ago, it seems a lot less noisy when crowded.
There is an excellent variety of dishes. The Thali's are a great deal and excellent if you want somewhere to start (i.e. variety in one dish), though I think they are only on Thursdays. We always share and get a wide variety.
The lunch buffet is a good way to sample a variety if you are not dining with
If you are unsure, ask for guidance from either the staff or other diners, though I don't think you can go wrong. All of the dosas (I think we've had all of them) have been great. The Uttapam fantastic. The okra is wonderful and has been thoroughly enjoyed by two okra-hating friends.
Cons: No cons of the cafe, Parking lot can get crowded.