Rico talks about adding performance data to method signatures
This is a very interesting article, is it possible that something as simple* as IntelliSense can help you write faster code? Tag method signatures with 'light, medium or heavy' and then simply don't ever call a heavierweight method than the one you are implementing. It's a start. The really interesting part is that Rico hopes to be able to publish the signatures.
*Conceptually simple, IS is a pretty hard problem.