This surprises me. Though I've used it with great success for several small projects, my only experience with SQLite on anything remotely large was a Rails app with maybe a million records in the DB. Over time, performance became very slow and switching to MySQL made a world of difference.

At the time, I attributed it to SQLite, but now I'm wondering if it was Rails or (more likely) my inexperience at optimizing performance of the app at that time.

It was about three years ago, though, so I am sure performance in SQLite (and Rails, too, for that matter) has also likely improved a lot during that time.