I am using VM for a while now, most of the time to have alpha, ctp, beta…
My issue was that my main VM was starting to be really big: 8.5Gb and I had to do something to save some disk space.
Some weeks ago I read about InVirtus VM Optimizer 2.0, and this weekend I was able to download there 14 days evaluation version. Installation was so easy and the result is that now my VM is 5Gb and loads faster. Great tool!!!