The Tartan 37 is a great boat! I've cruised and raced on one since the mid 80's. They have a nice balanced helm and are very responsive, handling a messy sea with ease. The interior is spacious and light in comparison to her big brother the T-41 which is very dark below deck. The cockpit is relatively big and has lots of storage under the seats.
The centerboard allows us to get into gunk holes that other boats her size have to stay clear of, it can be a bit tricky to lift when running, you have to winch it up very carefully between swells or it can get stuck, although I've only seen this happen once.
As a racer she does pretty well although she's becoming increasingly outgunned by the lighter boats. (She weighs roughly 16,000 pounds)
Properly trimmed she'll go 6-7+ to weather, and I've hit as much as 11 downwind but usually 8-10 with spin.
The construction is typical S/S, quality throughout the boat with a lot of attention function and making critical areas, easily, accessible. I went on board the 3700 at the Boston Boat show and I have to say I prefer the layout of the 37 much more.
The prices are starting to come down quite a bit, I've seen them listed from 65K-85k money well spent for a great boat.
Tartan 37 Sailing Association