Just decided to download build 40 today. No lag or frame choppiness beforehand. I started to play a bit, and it was all choppy and almost unplayable.
My computer will definitely run anything this game could throw at it, so it's not on that end. I started to change things one by one, and eventually got to drawfps. When I turned this off the lag disappeared immediately. This is the only setting I changed; not sure if anyone else is having an issue with this or not. When i turned it back on (changing nothing else) the lag returned, and then turning it off did the opposite. Not sure if its some sort of hardware issue, but it seemed odd.