Shaun blogged about the implications of caching - it saves db calls and cpu time, but needs the correct parameters (per language, per role) and additional memory and to be invalidated, when content changes, what is not always easy to determine. Compression costs additional cpu time, but saves bandwidth - which is usually the critical factor; notice haowever, that there are implications with several situations, most of them shall be solved in next version.

I have not tested pageblaster yet, but all I read, it is a valuable product for ASP.Net web sites in general. On the other side, doing compression inside the DNN framework has other advantages, as the framework often has additional information needed for doing it in the concrete situation. 

Hi Mariette,

Since you have a fair amount of traffic, my guess is that you recyle the app pool and someone visiting your site starts the reload before you do if you are seeing it in 5 seconds.
Also, having a dedicated server running 64bit OS, and only having a single application (more or less) on it is not quite the same as what most people face in a shared hosting environment.