Most underrated: Chek-Mate, easily. I'd have to say that it was intentional for the most part. The founders/owners never cared for the spotlight, never had a "look at me and all I've done" mentality, and generally just wanted to be left alone to work in a sport that they spent a lifetime loving and supporting.
Here's a little information about one of Chek-Mate's Founders. Something to brag about to say the least, but she never once mentioned it to me. I found out by accident.
http://www.sportshall.ca/accessible/hm_profile.php?i=25 The current owner, and bowyer for the last 25 years or so, has the same mentality. Although he is one of the best in the business, and has probably made more bows than any other individual bowyer (somewhere between 12,000 and 15,000) you'll never see him bragging about himself.
Most overrated? Of course some names come to mind, one in particular, but like some others I don't care to post it in public. Word gets out sooner or later anyway.
I will say that when I hear someone say (or see it posted) "you can't go wrong with this bow", they are overrating it individually. There's no such thing as a bow that is perfect for everyone.