So I thought I'd post my experience.
Setup was pretty straight forward. I haven't had a whole lot of experience installing and configuring Linux stuff, but the HOWTO Wiki was pretty easy to follow. I did miss having a guide on how to get it into the startup processes, but I did some googling and figured out how to create a simple script and add it in.
So far I have the domain controller up and running, domain users being able to authenticate from a Windows Vista Ultimate machine. I instituted some group policy management to control log-in times for my 10 year old. I was disappointed to see that Windows Vista does not allow Parental controls on domain users. One of the reasons for setting this up was to make it easier to allow my family members more ready access to other computers in the house. Not having a way to manage this for a domain user means I'll need to implement some controls in Linux.
I'm thinking about putting up a DNS filter on the Linux server, which I think will require a different DNS server instead of the built-in one that came with Samba 4.
I've also had problems getting profile space active and storing from the windows machines to the profile directory I setup (per the wiki HOWTO). Any gotchas that I should look out for?
Also, with Samba 4, samba users do not have to have a local linux account. How do I manage file/directory permissions for samba users?