I held off on upgrading to 6.5 until two days.  One of the first tasks I tried in the HTML5 client was assigning permissions and it did not work.  It works fine in the Flash client.  I opened a support request as was told, "We do NOT recommend using the HTML5 for production use anyway if you do encounter any limitations or issues with it, it will be more than likely because it is in beta."

And in another reply from support I was told this,

"Hello Mike,

I wish the HTML5 was completed since the flash based version is so slow and inconsistent. We have the option to use the HTML5 and by all means use it as much as you can, but if there are tasks or changes you are not able to do in that it is standard process at this moment to use the web based version instead - this is what I mean by supported.

As for the 6.7, it is ALMOST complete. Roughly 90% of the things you an do in the Web Client can be done in HTML5. 6.5 is roughly 80% complete.
I imagine it should be completely done by 3rd quarter. I hope.

Let me know if you have any other further questions or something is misunderstood. "