I've written about Hamachi as a lightweight VPN solution in the past and for a year or more I used it every day to access files at home and provide an in to friends and relatives machines who I do tech support for. Not having to worry about opening ports on routers etc. is fantastic but recently Hamachi got unreliable and now I can't make it work for more than a few weeks without upgrading (due to their new license) which is a pain as suddenly you can't VNC to the machine you need to upgrade!
Anyhow - I've been playing with Leaf for a few days and it seems a much more solid solution. It also has the advantage of having routing built in so you can use it to expose other machine on the target network over the VPN tunnel. As well as allowing LAN play across the internet for XBox games that don't support Windows Live I imagine any embedded devices you don't want to expose to the world over an open port would be usable from wherever you've got your laptop (insecure wireless in a coffee shop, for example).