You won't be charged for data transfered with your reverse bt dun connection as long as you don't have a fallback network connection specified. You can find that setting, if available with your carrier, under the Network part of your prefs, after pressing details at the bottom of the page: Prefs>network>details (Hope that wasn't too confusing >_<).
Pros and cons come with just using your at home connection. First con of all being that you can't use your internet functions anywhere but at home. The major pro, though, is that you drop that hefty data plan from your wireless bill.
Goodluck setting it all up. It's fun to play around with, if anything. The thing I like most about it is I can browse my favorite web pages while my computer is being used.
