I own the Contigo and totally love it. It's probably as close as you can get to spill proof without a screw-cap. I've dropped that mug so many times and never lost a single drop. Make sure you release the pressure inside before trying to drink something really hot because pressure builds up inside!
JulianI have several Contigos. It does a fabulous job at keeping hot stuff hot. When I use one for coffee, I've had the coffee remain drinkable for 3 hours or more.
The only real problem I've had with them is that the lid can be hard to clean. The newer lid designs that open the mechanism up for cleaning has resolved that problem.
EWTHeckmanI have a couple Contigos and a Zojirushi. The Zojirushi is much better. Keeps stuff hot longer, and the lid disassembles fully for reasonably easy cleaning.