"Shortfalls" might be too harsh of a word.
It hit me that it was a shame that, since it's called a "280," that it doesn't have 2 - 140mm fans in front (and also the top), especially since it's large enough to accommodate them. It's a very cavernous case, but if you happened to fill it, it couldn't keep its contents cool. The fan controller on the back and how power has to be run to it - is - just - wrong. It just seems to be another nice idea by Antec that's just not finished.
I still think the P280 is a wonderful case to work in. It has many of the features that I'm looking for in a case, like sound deadening, filtered ventilation, I/O that faces forward, not upwards - like Fractal Design and Nanoxia and clean looks.
At first glance, the P380 looks like they mashed a P280 and a H440 together. And failed.