The Advanced Open Water Course does teach new skills/procedures as well as expanding on skills leaned in OW. It depends on the dives you pick to do. But, it is not an in depth course on each subject dive. Consider it more of a smorgasbord to give you an opportunity to try different dive environments or skill sets with an instructor close by to critique you. The five dives I took were Deep, Navigation, (both required), Search and Recovery, Wreck and Underwater Naturalist. I really enjoyed all of the dives. The dives that I got the most benefit from was the Navigation Dive and the Search and Recovery dive. Lots of compass work between the two of them plus tips on natural navigation. Our instructor made us repeat the skills until we were able to complete them successfully. The Wreck dive was also interesting as it taught me to be more aware of the environment on and around any wrecks I may dive on. Deep Dive was not all that exciting (dark and cold, nothing to look at) although actually doing a three minute safety stop after the dive and the tips given concerning buoyancy control were very helpful. Underwater naturalist was OK (Fresh water fish and critters are not as interesting as their saltwater cousins).
I recommend Advanced Open Water for anyone interested in expanding their dive experiences or who think they may be interested in a particular skill but are not sure if they will like it. Try that skill as one of your dives. If you don't like it then you won't waste your time and money taking that specialty course.
Hope this helps. Dive safe.