I couldn't live without the taskbar menus that show the contents of a folder when you press the double arrow.

Unfortunately, when you e.g. have the computer folder as a whole in a taskbar menu and you browse to a folder that contains tons of files, like the fonts folder in windows, the whole explorer is hangs badly for a while.

If you are aware of this behaviour and you remember which folders contain buches of files, you can avoid hovering over those folders to work around the issue. Otherwise Explorer just hangs.

As I found out, it takes Explorer a timespan proportionally to the amount of files in the directory to unfreeze. I have a directory with about 22.000 files - you can imagine how long it takes to get usable again - some minutes!

This behaviour is highly annoying and needs to be fixed - don't know if anyone except me ever has noticed it...
It has been in all versions since they first introduced the feature with the quicklaunch thing, I think...