Hmm, in our office we have the whole kit an' kaboodle as we are a dealer. This includes the teleworker, office suite and ipsec vpn blades.
I have installed a few sites with just the telworker blade and some with just vpn. The specs for pc's vary depending on the application, but if you get anything current i.e. 1.2ghz or more and 512 mb ram 80gig drive, you'll be able to run just about anything on it.
A lot of our customers, ourselves included use dsl to connect to the net or the server and the client side. With dsl you just have to be ware of how much bandwidth is being used. Easch teleworker set uses about 50k. Some days my teleworker set is very poor at peaks times in the office, as people are checking email, etc. For 6 months or so we had one of our call centre agents using one in Vancouver, (we are in Calgary), it worked pretty good and only ran into probs when there ware heavy traffic on either one of our networks.