A while ago, my guessnet setup started messing up, just before a business trip, and I did not have the time to debug the error. After a quick consult on IRC, I installed and configured laptop-net, which worked.
While I had a working package that would let me carry my laptop from home to LUG to office, and various trips with Hotel networks once in a while, I always had to tell the system which scheme to use, since several of the networks used similar IP addresses and topologies (welcome to the world of NAT). I have never been comfortable with the fact that laptop-net did not consider MAC addresses while making its determinations.
laptop-net, on the other hand, is like a combination of ifplugd, intuitively, and switchconf, except better since it is all integrated and works seamlessly. guessnet does seem to work better for me, though, if for nothing else since it can actually determine where the laptop finds itself. I have successfully integrated guessnet in with ifplugd, and made sure that things play nice even with hotplug in the picture. So I am a happy Guessnet camper once again.