Adopting a ring strategy is good and needed, but choosing the right one for your organization may be trickier than you think. It concerns me to some degree when I hear that fellow workers are going to be testing software for MS. They then need to make know that there is an issue with the product and what that is before the next iteration goes to the masses. That is quite a responsibility to place on some users. I have been caught in the middle of "it is fixed in the next release" so no fix or workaround will be provided.
For a large company, perhaps utilizing all those rings make sense. but for a small to medium company 2 or 3 rings may be the best option. I am toying with the idea for Office using the Semi-Annual Targeted version for the majority of folks, as that channel provides the monthly fixes. My point being there are many ways to implement rings without being locked into one particular methodology.