focus on performances
even if there are a lot of ways to increase, we must admit that symfony is not the fastest framework by default, and we should therefore focus on making it faster
+1 with Benjamin. The performance problems mainly come from how the framework is used, not the framework itself.
i'm with benjamin.
i've not been finding symfony's performance to be hurting in any sense - all my profiling has shown that all useful optimizations have always been in the application logic.
as for ORM level caching, Propel 1.3 supports this (not sure about Doctrine). there is a memcache plugin, but since it has dependencies on your PHP build, i strongly suggest keepin them out of core.
Benjamin Meynell commented
I wholeheartedly DISAGREE that performance should be a top priority. There are a myriad of things one can do to improve the performance of one's application. Symfony is NOT the bottleneck and this is PROVEN in the REAL WORLD with top 100 sites running symfony (Yahoo, DailyMotion, and maybe others...).
Gavin Love commented
I would say the main area to focus on the caching system, better integration to memcache or APC etc and better caching at the ORM level.
For example today I realised the pager->getResults() always runs the query even if nothing has changed so i had to add a wrapper to cache results
Performance optimization should be done in cooperation which real case high traffic applications.