This! Especially f'in dropbox.. swear to god everytime you try to click on a file it does some type of request to try to "help" you.

Which is fine, but it gets slow as hell. I have a brand new very fast machine and all the sudden explorer was getting so terrible. I downloaded something to disable the dropbox shell extensions and back to very nice performance.

Still it's sign of bad design IMO. Proper design would show menu immediately with some indication that some items are still loading, while running shell extension callbacks in background. But probably that's too fundamental to change at this moment. I remember entire Windows shell freezing because of similar things back in Windows XP. At least now different shell parts don't freeze all at once.

“autoruns” from sysinternals

ShellExView from Nirsoft