I agree with Chris. We did an igloo camping trip together back in 2007 and we learned a lot about the utility of igloos. If you plan to basecamp in a nice area for several days its worth building an igloo, but an igloo doesn't work well when you are traveling because it takes too long to build.
In the wintertime its hard to get an early start, travel to a destination, and build an igloo. So you end up taking a tent for shelter until you get an igloo built. Building a larger 11' igloo with the Icebox tool can take up to 6 hours, so you have a large time investment. However, Tad's method requires less carry weight and takes less time.
All that said, an igloo is worth the effort if you are going to base camp for several days. An igloo is wonderful for winter camping in really cold, windy, or snowy conditions.
Here are links to past articles we have published on igloo building: