There is another guy who is trying to get 3 or 4 separate sites communicating well - For him, this is probably also the best / easiest option.

But easy is relative - Maybe he will see your post and ask your instruction.

I was talking about the TINC package.

That is very, very cool. I've added it to my list to try as the first solution.

EDIT:

Wow, that was super easy and works very well. I think I'm going to use it.

Have you considered a full mesh network VPN?

I'm not sure what that is and what I found on Google isn't much help. Can you elaborate?

I take it a nice layer 2 metro-e between the two is not an option?

That would make my life so much easier, but is not in the budget … yet.

OpenVPN tap connection.  I'd try and do without it if you could though.  Why do you need the same network on each side?

We're using Hyper-V replication to replicate a bunch of VMs. It will be much more seamless if I can just power them on without altering IPs and so forth.

Does tap bridging work with 2.1? I thought 2.0 or 2.1 broke it?