I noticed that it works here, however - I get a blank page on my install. 

Can anyone else confirm this?

Same here since beta 5 upgrade. It worked up to beta 4 for me.

https://www.youtube.com/watch?v=GaQJB_bWA4c

 

Only works if you press enter after.  I HATE THAT.  Ok, hate is strong, but I thought they fixed that.

Test:

 

https://www.youtube.com/watch?v=VrKNb5uwjxQ

 

 

This youtube url works:

http://youtu.be/VrKNb5uwjxQ

 

Yeah. youtu.be links are fine on my site but youtube.com links aren't

It appears that http:// youtube links are working fine, but https:// links are not.  I'll log a bug report.