And while fast, ride like shit when not going fast or in rough water (feels like being on a bobbing cork, instead of the normal rocking motion of a traditional ship). Never mind the other issues of docking during high wind, no troop berthing, no CIC, etc.. I spent way too much time on those turds, doing experimental testing on several concepts of operations. I can tell you though, they can get from Key West to Belize in no time at all (hence no troop berthing, just rows of airline seats and rifle racks bolted to the walls).
BTW, they're not Navy ships either, they're actually "owned" by Military Sealift Command (MSC). Makes for a weird command structure with a civilian (MSC) captain and a military Commanding Officer.