I did not install Flash on my 2011 MBP and for the most part I have not missed much without it. For YouTube videos I have been using a Safari extension that supports HTML5 videos, but that didn’t help me with the DEVON products. I just discovered today that there is a HTML5 trial available for viewing YouTube videos. SIgn in with your YouTube account, opt-in the trial, and you can watch YouTube videos from DEVONagent and DEVONthink.