That's likely a false impression, and has to do with things like number of database calls, design, and other non-language-defining features. Don't let perceived speed be the deciding factor in your language choice: If speed was that important, you'd be writing in C.

When I first started using Django, I wasn't sure about it either, for a few different reasons - but performance wasn't one of them. Long story short, I'm glad I invested the time in taking it up...

Django was actually my first use of Python - so you can imagine how pleased I was to replace a custom PHP app with something I just learned - and in record time. (if you're interested, the web app was: http://www.snapact.com/)

I have noticed no issues with performance as compared to PHP.

This is an old link (that I wish would be updated) about performance of some various frameworks (in various languages):

http://www.alrond.com/en/2007/jan/25/performance-test-of-6-l...

Perhaps it is possible that Django's highly flexible nature is giving you enough rope to hang yourself here. Performance is not an issue for me, though (as always) I have to be careful not to do stupid things to the database.