Does anyone else experience this?

I have 4GB of memory, but I constantly will have ~1GB of inactive memory, which Apple and bloggers and fanboys claim is part of a great Mac OS X feature and will be reclaimed if the system is in need of memory.  Well, if I am out of free memory but have 25% inactive memory and try to open Word 2008 for Mac, it takes 5 to 10 minutes to open because the system gives it no memory!

I know that with the development tools, I can type "purge" at the command line...but how do I get my Mac to automatically give back inactive memory when I really need it!?