Jay,
I did EXACTLY what you are wanting to do in my company. I have a small engineering company with offices in two towns separated by 80miles or so.
We work primarily with AutoCAD files.
I can tell you this from my experience: What you are wanting to do is not easy to maintain with SME Server. Here's why:
1. It is no doubt desirable to you, as it was for me, to centralize user authentication. There really is no easy way to do this for two subnets, connected by a WAN, with SME Server. You'll either need to have a single SME server at one location, meaning the remote office will be authenticating across the WAN. Lose the WAN and your users won't be able to log in to their workstations. Or, you'll need to have an SME Server at both locations so both subnets can have local auth, but the difficulty is how to keep the two sets of users accounts synchronized.
If you can setup a reliable VPN connection between your two subnets, then you'll likely have the best success with a single SME Server providing auth for both subnets. Again, the WAN is the weak link here.
2. The files you are working with are too large for users to pull back and forth across the WAN. Therefore, the best solution is to maintain identical sets of data at both locations. I did this using the utility Unison. I created a set of perl scripts that I'd be happy to send you that syncs ibays between SME Boxes at desired intervals (I used once per hour). There is a slight issue of a user modifying the exact file at both locations at the same time, which can cause some sync issues. However, this issue is managable with some protocols to your users.
Also, have a look at my recent work with smeserver-adv-samba here:
http://wiki.contribs.org/Advanced_SambaThis wiki document provides some functionality that will be of value to you and it also relies on updated e-smith-samba packages that provides updated WINS functionality that enhances network browsing across subnets, which is what you are going to need between your two subnets.
There are just a few thoughts. I just want to impress upon you that using SME to tie two offices together with the types of data you and I work with is not for the faint of heart. Proceed with caution and only deploy your solution in production once you've field tested it.
Greg