Greg,
I have worked for organizations where VPN was used for teleworkers/commuters. In all situations there was a slight to large increase in latency and a small percentage of time when there was total loss, which could never be explained. In all environments, the network management was hidden, meaning we never knew when someone changed a setting or if their were repairs going on during the failures. Generally, though, VPN was fairly reliable using http:// (non-secure) settings. VPN does increase the points of failure, as you are now adding the settings for the VPN pipe, and any local network the user is working from.
A direct/wired connection is important when using VPN since it is hard to diagnose additional issues a user may be experiencing at his or her location. Unless VPN is a permanent solution for the user, and he or she teleworks all the time, the user should avoid uploading large CAD objects through the connection and checkin when connected to the LAN.
