Try using the DeBug layout option rather than preview. It can tell you a lot more than we can about performance.
Yesterday I just popped it up to see how the debug operates. I was able to fix 6 HUGE oversights by me. (one that was spawning 200+ additional objects because I forgot a "Trigger once" block!).
@Ashley really made a nice tool for us. I have a few other commercial game engines I develop with. None of which give the user so much insight and control.
He even made so we can Peek and Poke values into the Global variables, so we can tweak stuff during runtime!
The big delay might mean you have a similar problem to me. I could not see the extra 200 objects because I am using a very powerful gaming rig (4Ghz OC'd 8 core CPU, nvidia Titan 3 way SLI). The extra 200 objects are nothing to this rig, but it would probably set a netbook or tablet ablaze.
I am glad you asked here. I have been looking for an excuse to rave about Ashley's awesome new tools for us!