What are your system specs? Desktop environments will consume more memory if it's available, within a threshold. If you have a lot of memory available, it would explain why its' trying to use more.
I just upgraded to on a virtual machine with 4GB and it's using ~500MB at idle. For comparison, Core uses ~945MB. I took this screenshot right after a restart for good measure, but from here the real consumption would probably spike as more and more tasks use the memory (which is a good thing, otherwise it's unused memory).
