I have flown Estonian Air (OV) several times in the past, both Economy and Business Class.
Estonian Air flies with B-737-500 Aircraft leased from Maersk Air. The Cabin Layout is quite nice and there is much more room than on Lufthansa for example. The food (you get a decent meal on the 2 hour flight from Frankfurt or Hamburg to Tallin) is very good and the flight attandants are quite interesing (They are nice but have the little cold touch from the East!)
Tallin Airport is also quite nice, small but modern!
Anymore question, don^t hesitate to contact me!
P.S. Would always prefer OV