Performance is definitely the issue, we all knows that, but despite of that is PLSQL Developer one of the best tool of the market, so, we have to try keep calm everytime hellish delay happens smile (and some days its pretty often smile
In my opinion problems are related to connection handling, multiple connections are more "addition" than integral part of application (why is there some "main" connection?). The hell comes when you try to use more connection at the same time and some of them are not available (eg you discconnect the vpn...) even if you tell the developper to close the connection, it sometimes "try" (=at least 30sec timeout) smile .. Another problem is poor tuning of system/dba queries (to get the oracle catalog data), you can try the checkbox "use DBA Views if avaliable" but it doesnt help much.
But as I wrote, for developer there isnt something really better smile