Agreed: when a choice of Citibikes is available, I always choose one with a NuVinci hub. And yes, very rarely I experienced the same failure mode you describe. Also very rarely, the high end of the shifting range isn't available. Comparing the NuVinci, Sturmey Archer, and Shimano hubs, the Shimano is my least favorite, but of the three hubs, the Shimano is the only one that - for me - has been 100% trouble-free.