Get a better PC. Its running smooth and fast on mine. The editor is optimized else you wouldn't be able to use it as a dev-tool - though I know of dev tools that can drive you nuts.
You should at least have 8gb ram for the editor, 64bit version of windows goes witheout saying (yet I said it again) and a decent cpu!
How charming.
Let me see.. hmmm, I have a core i7 with 6 cores running at 3.3 ghz each. A very good GPU (Geforce GTX 580M, more powerful than their Recommended GPU) and loads of free space on the hard disk. Oh, and 8gb of ram and 64bit Win7. The game autodetects as "ultra" for quality. I cannot see the 1920x1080 option, but that is a minor issue.
Despite this, I still find the occasional stuttering in-game and load times are still long.