I swear by the Communications Specialties Scan-Do Pro Ultra. Against an Extron and a Sony ina shoot-out, it won in a walk-away. Very responsive service too, e-mailed a query, the VP of the company called me back!
You should check out the TVOne solutions as well. I talked with the VP at NAB and their products are real solid performers. I will be deploying 2 CS-620A scan converters in my control rooms real soon and a few video scalers (SC-1250) as well.