I am not sure about Gallery 2, but it would be very nice if there were a version of Gallery available that used MySQL. I find it very difficult to navigate through the album permissions, etc on the back end. As well, I use gallery embedded in PHPNuke, which has most everything in the mysql database. Maybe this is how g2 is being developed, I don't know. I haven't taken the time to read up on it.
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G2 will support MySQL, Postgres and Oracle. Probably more as well, as custom storage modules are created over time.