This build seems to have performance problems too. Like, sometimes I get 5-10 fps, then I get 60 fps... I haven't yet figured out what causes this. I just had like 20fps for the whole day, now I changed one canvas object to 50% opacity and boom, 60fps, no slowdowns. This doesn't always work though, but it must've done something.
Though during the last couple of versions, I noticed that there were still Construct Processes running the background when I closed the program, which slowed down the computer.
Also, I use dual screens and if I have Firefox (or Songbird, curiously) open on the second monitor), the performance drops a LOT as well.