Just wanted to add to the discussion... I too, for a long time, noticed high memory usage. As someone mentioned, when Windows has free RAM it will try to use it. So until now I kinda turned a blind eye.
But today I noticed a lot of video playing problems. Task manager showed me the hard drive was crazy busy (SSD; >300MB according to task manager performance view...!). GW was as the root of it. I have 2 dedicated video cards with their own RAM. Should be good enough. i7 processor. Currently not running any torrents (but I am running VPN tools).
I am running Windows 10 but currently am still low on RAM (only 4GB; I plan to buy a lot more soon). Which could explain the hdd problems... Windows is swapping, maybe.
When I stopped the service, everything went back to normal. I have GW installed for quite some time now, but did not find a cleanup log. Using version 1.067b.
UPDATE: now updated to latest version 1.1.32b. "Process" in Task Manager now shows about 70MB hdd usage. Mem is about 450MB, still.