if you want COPY support from the JDBC driver just for performance reasons, you should probably also consider using the driver's batch mode. Please have a look at the following links:
Encoding is a serious consideration. While testing pgBee, I ran into problems inserting codepage 1252 files into a SQL_ASCII database, because of character mismatches. In your Java application, you may specify a particular charset for reading the input files. I haven't used the patch, but if support for the COPY operation is to be included in the driver, please make sure the driver handles such things with care.
It might also be that the driver shouldn't have to deal with things like that. It's a driver for connecting to a DBMS, not a backup-restore solution. But I cannot speak on behalf of anyone or anything, I'm pretty much an occasional pgsql-jdbc reader.
