Moving Active Directory computer to another OU - What are the affects?

If you have no GPO setup at all, then nothing should change. This will just be a sorting within the AD for you. Once this is done it's a great way to then start to use GPO's to lock down things.

When we did something similar we had our LDAP users start getting failures as the DNs had moved on them. It was an in house ap though, so you may not have that problem.

You should be fine with moving them; we've been doing it as a matter of standard policy for 8 or 9 years now without a problem. Just don't move your DCs, that's all.