Along several years doing mobile development the main thing I've learned is that a mobile device is a resource constrained device, and it will impact directly and inevitably into our software architecture. Part of the problem are the small storage space and the limited communication bandwidth, and trying to tackle both problems a very good option is the usage of compression tools, but moderately, we should keep in mind that compression and decompression are processes which require processor and can be very expensive in terms of resource management.
The .Net CF 3.5 is the first version that includes compression support out of the box! In the past we had to rely on third party libraries or, what is even worst, build our own compression library.
It's indeed a very nice and expected addition to the .Net Compact Framework. Now it's time to start using it!