http://bentasker.i2p/posts/documentation/security/98-automounting-samba-shares-over-openvpn.html
It's very easy to do manually, but most users don't want to have to learn to map network drives (or shudder use some of that commandline black magic). Thankfully, they don't need to as you can tell OpenVPN to do the legwork for them; A minor downside is that this can't be configured on the server (which makes sense as the commands needed would differ between each OS), and so needs to be configured for each client.