Really if you think about it TS Gateway is a function of 2008 Server which was a great addition as I have customers who uses this a lot. They also use the Published Apps of 2008 Server which is another story. With SBS 2008 the connection to the client computers is driven by TS Gateway through the RWW page. This is a great fall back position so if your RWW page ever goes down you can still get to the server or client workstations through the TS Gateway piece without going through the RWW page. One thing you need to make sure is that the client connecting from home has XP SP3 or Vista SP1 on their workstations or has RDP 6.x so I would really suggest purchasing a certificate for your SBS Server that way this is covered and you do not have to worry about getting the self signed cert imported onto the home client even though this is covered well on how to do that with SBS 2008.
Another part of 2008 Server running in TS Mode is the Published Apps piece running on a 2008 Terminal Server. The great part of this is you can select a application and create the RDP for this app and then present it to s remote user without giving them the full TS desktop session. Not all will work this way but most I have found will if they will work on a TS Server. Just have to watch if they have any switches in the path to launch the application. Or you have the web page that you can connect to and do the same thing as creating the RDP file for that app. All these works great if you have a SBS 2008 Server with a 2008 TS Server in your domain. Even if you don’t you can do the same thing here but the SBS 2008 and a 2008 TS Server is one scenario we will have as we have customers running SBS2003 and TS 2003. I have even went so far as to link to a Published App off the RWW page and not have to send the RDP file to the user. It is all a matter of how it fits your customer’s needs.
Til Later just Roger