As far as the most stable, and recommended version of the Solarwinds modules - does Solarwinds just say "the newest version is the best"?
Or, are there slightly older software versions of some that are regarded by the majority as the most stable and preferred of each?
SolarWinds is like clouds - you lay down and you watch and follow them - and it would seem like not much changes. The moment you close your eyes for just few minutes - the whole thing changes so dramatically - you will not even recognize it 
It is one of very few companies ever releasing Major versions at least twice a year. They do have a lot of development going on (click on PRODUCT ROADMAPS button above to get an idea). If you will stick to the old "stable" release then it will become "very very old" pretty soon. Of course there are some bugs etc - like with any other products, but so far those are really minor and simply cannot compare to the whole lot of new features and improvements with every release. So, just go for the latest and keep up with updates as soon as they arrive
