Strange that you find it slower. Microsoft has a very rigorous release process (I've been directly involved with it) and the release candidates were "code complete" some time ago. They most certainly have not bloated it nor added "memory checking at the code level". Have you run the Windows Experience rating or other benchmarks? There are many things that could cause the RTM to run slower than an RC and it might be a fixable problem for you.
I think the blame lies squarely at the 3rd party manufacturers and their software writing skills. It's deplorable that Adobe for instance doesn't have a 64-bit IE8 plug-in available. I've also noticed the Sun JVM give problems with certain installs. I'm now also trying to troubleshoot a video performance slowdown which only manifests itself as minor jerkiness in YouTube videos which is probably their fault too.