OSX Mavericks using up RAM
Mavericks' new memory management tool was designed to do exactly that, use AS MUCH RAM as possible. See, "free ram" doesn't actually do anything until it's used. It's just there idle, waiting to be allocated. Mavericks uses physical memory much more in order to speed up actions. For example, closed applications and file will be cached until memory is needed, at which point they can be overwritten.

For example, my 24GB machine currently has around 14GB of file caches (after around 5 weeks of uptime). In total, 18 GB of my 24 is used. This demonstrates Mavericks attempt to cache everything possible. If not for file caches, I'd only be using 4GB of my 24GB of RAM, basically rendering 20GB (~83%) of my system memory (costing well over $300) as completely unused.

I don't think your performance issues are a result of the new memory management. If anything, there should be decreased disk access, faster load times, etc. You can try troubleshooting by running sudo purge in terminal to force the deletion of file caches and inactive pages. (Note: Free RAM ≠ faster performance)