It only stores very few items, but well if you pump them out somewhere else 9 slots is pretty much enough.
Not for me, I like to build processing plants that can handle huge peak volumes, my last major build could process* in real time the output from 24 fully powered quarries. To do this I had to design and build item/flow regulators and much more besides, the ender chests as a 3x3 is way too small a buffer space, it could be filled in one tick (and would extremely like be filled in one tick) and I need a space much larger than that per tick (i.e. even if I empty the entire chest every tick, in the very next tick there would be more items than the 3x3 could hold, so my entire system would backup and be limited by this bottle neck.)
I'm thinking of other designs, which is cool I guess, but what I intended to do with my next major build was to push on to being to handle in real time the output of 64 mining turtles each mining one chunk.
The problem so far, is that every design I've come up with so far that does away with or deals with the ender chest nerf will cause way more server load.
*sort, macerate, sort, furnace, sort, do something with stuff, sort, autocraft, storage etc