My 2 Cents.
1 - I have a yearly sub to AMR, and I use it for me ENTIRE guild, and I use simulationcraft to get the best stat weights for everyone. (Oddly enough, my resto shaman is now haste/mastery and is TEARING SHIT UP)
2 - It's also very useful for little things like what to upgrade, what to use bonus rolls on, and where to get gear.
3 - Do not use the default stat weights, take some time on wowprogress or worldoflogs, find what stat weights are the best, (Just a basic priority order, you dont need super precision) and put them in.