[Samba] Samba 4 in production?

[Mark Rutherford]

  I have read many stories and testimonials from people that are running 
Samba 4 in production.
This encouraged me to try it out in a couple of virtual machines and, as 
expected I encountered no problems that
I could not overcome. (mostly DNS setup issues)

We are running 3.5 right now just as a plain NT4 domain controller with 
DRBD and friends.
This setup has worked for many, many years and the possibility of 
gaining AD is very appealing.

When I tested Samba 4, I joined a few Samba 3 servers to it and used 
resources from those servers without any issues.
How are others using it in production?
Any pitfalls to using Samba 4 in this manner?
Anyone care to share their stories, good or bad?

Thanks everyone.