In Npgsql, the .NET driver for PostgreSQL, we've switched from simple to extended protocol and have received a user complaint.
It appears that when we send two messages in an extended protocol (so two Parse/Bind/Execute followed by a single Sync), where the first one creates some entity (function, table), and the second one can't query that entity (not found). This isn't terribly important but does seem a bit odd, I wanted to make sure you're aware of this.
Thanks,
Shay