Mavericks unusually high RAM usage I thought Mavericks was suppose to utilize RAM memory better, thus run smoother.

Running ML on Mac mini 2012, with 16GB RAM...always running smoothly even with over a dozen apps running.

Now, after installing Mavericks, my Mac is SLOW, eating up RAM like crazy! Looking over usage, of the 16GB of installed memory...on average it uses 10-14 GB RAM when barely running a few apps!!! 

There is this kernel_task that is always running with over 1GB of RAM and most apps are not taking that much RAM, so what is using up all my RAM?! File cache? It shows very high in that new description, with about 1/3 of my total RAM
Who said that this memory use is bad in any way? At the very least, the OS will be using the memory so that it can spin down your hard drive at the first opportunity. Hard drive access is energetically expensive. RAM is already powered up, so letting it sit idle is truly wasteful.

The question is a yet another post in the style of "oh no my ram is all used up, bad [insert your bogeyman here]". Let's get it out of the way: RAM should be always fully utilized. You paid for it, you're paying to keep it powered up, it's really counterproductive for all this money to go to waste.

If your computer feels slow right after updating, it's true that the indexing service may be to blame. Let it stay on overnight, make sure you get a full Time Machine backup done, and see what transpires next. Don't get hung up over RAM consumption - without some rather technical understanding of what those numbers mean, you can't make any use of them. They are red herring. It's a curiously recurring pattern.