> As well as the performance/security issues others have raised

Did you see any issues if connected via zebedee ?
We use this solution for some of our apps very successfully.
Zebedee does a very efficient compression and as we do
most processing via stored procedures on the server side
we do not have any performance issues although we handle
mid size tables (about 1 Mil. records).

Security should not be an issue if you use keys for
authentification (also supported by zebedee).

> 300 concurrent users, you might want to consider using a 'middle
> tier' on the server side.

For such a huge number of concurrent connections this might be the
right decision.

Regards,
Frank.