I've been to the place in Harvard Square, and have had pretty positive experiences. The optometrist is nice, I got a complete pair of glasses for about $99 once (they're the thicker plastic, since I only wear contacts if I'm going out of the house). That said, I always buy my contacts online because CE's prices are high (like everywhere else). I first went there because they're a local business and I like supporting local businesses--I think they're larger now.

I have a friend who went to 241 Optical (http://www.yelp.com/biz/241-optical-cambridge) in Harvard Square recently, and she really loved them. Her glasses are really cute, and I think that's where I'd go if I wanted anything beyond a basic eye exam and contacts prescription.