Paul,
Thanks for your interest in fingerprint solutions from The Echo Nest. You have a clear grasp on the differences between ENMFP and Echoprint.
ENMFP provides coverage of the entire Echo Nest song universe but with closed-source libraries for code generation.
Echoprint features open source code generation, its strongest quality. While it doesn't include every song we know about, about two million songs are included in the current database, far more than had been originally listed, and the database is refreshed fairly regularly to keep the hottest and freshest songs included. For your scan-and-match tag cleanup application, over-the-air matching is not an issue.
The community contribution tool along with increasing the coverage and accuracy of Echoprint are all in our plans, but we don't have any announced timeframes.
~David