While I'm a staunch proponent of building code that reuses other work as much as possible, there comes a time when new ideas, implementations, or just plain better work means either your dependencies are co-dependent (ha) or simply obsolete.
If you're interested in doing code profiling, KCachegrind is a great utility to investigate what part of your code is hogging CPU time. If you're on a debian or ubuntu machine, it is simple to install. If you're on OSX... well you've got a bit of work to do.
When Media Mover was first under development, it was started on an already obsolete version of Drupal. Now with RC1 due any day now (next week, I swear) I've realized that I can't wait any longer to start moving toward Drupal Six. So I've started the porting process and of course it is not an easy road.