Having just had to move out of a much loved Brownstone rental in Clinton Hill because the house was old I can tell you from first-hand experience: NYC is a seller's market right now. We had anticipated to be able to stay in our apartment over the summer as contracts were signed and paperwork submitted, but ended up having to move out within a month due to a cash offer being accepted.
All cash offers above asking price are the norm for some sought after locations in New York today. Things are moving fast and it can be hard for buyers to keep up with the pace. The New York Times has an interesting write-up of the situation and also offers some advice for buyers.