Prior to downloading and installing the latest release (74), my project worked perfectly and the fps was 65~70+ with little issue.
After updating to r74 my FPS took a hit. I noticed the preview configurations for projects were changed and that the group names I have were rewritten and named with numbers. The next thing I noticed was that I could not use the system "compare to values" function without it disappearing after saving and reopening my project or when I would C & P the same condition twice.
The last thing I noticed as well was an issue with turning a layer invisible or visible with one button toggling it ("I" for inventory). Sometimes it would work but then the events would disappear and other times, mostly, it wouldn't work at all.
I know this was not as thorough as possible but I figure tossing this all together for now should bring some attention to these issues. (I've also tried with a free new project to recreate these errors and they do reoccur)
Chrome & FireFox
Win 7 64-bit
16 gig ram
nvidia 850 GTX (latest drivers)