I've even used a Citibike to go places when I have my own bike parked at my office. Locking/unlocking, plus getting the gear in place just isn't worth it for a 10 minute ride. I just grab a bike from the rack and drop it off and never have to think about it again.
I don't know what the plans are for NYC bikes over the winter. We sometimes get a lot of snow, and sometimes don't. And then of course last year there was Sandy, which nearly killed the program entirely when the storage area was inundated.
As for riding in Seattle, these bikes are great for flat areas. I wouldn't want to ride up Cap Hill or Queen Anne on one of them. Even on my Davidson, I never rode up Queen Anne, but I lived up Capital Hill so I did it all the time.