|Cast of Players in progress|
I am very excited about including Cast of Players in my Eldar army. It has driven me to consider formations more broadly.
|CAD & Allies Detachments|
Small and medium formations and army specific detachments I think transform list and army building. The army specific detachments enforce a level of fluff onto armies, while the formations go even further. Formations, especially those with varying special rules, impact army design. Some units that are sub-par in a CAD become good options given a formation special rule. These special rules can be unit, if not army, defining allowing the formation to accomplish table-top roles they otherwise could not perform.
On the hobby side, smaller formations allows hobbyist to build out a complete somethings without having to invest in a full army. The willingness to invest less than a $200 in a playable combination of units (to include the book) is nice given the current costs of buying a complete 2,000 pt army. These are also much faster to paint, again giving that sense of accomplishment sooner, rather than always distant.