Could be wonderful - unfortunately pretty average!
I've stayed at the Hotel 57 a number of times and feel able to make some pretty balanced statements about it.
You're experience will (obviously) be directly impacted by the other events going on within the hotel while you're there.
For example - on one stay you would have thought that I was the only person in the hotel(!), whereas my most recent visit I struggled to find a seat in the bar....
As usual for a Manhattan hotel, try to get the highest room you can. from about the 10th Floor up you'll be lucky to hear any traffic noise.
Do not expect anything except for slow service at this hotel though. The staff are friendly and sociable (perhaps a little too sociable!) but getting served is always a drawn out process. If the hotel is low on customers - then there aren't staff around, if the hotel is full - then they're all rushed off their feet. There doesn't seem to be a middle ground.
The rooms are pretty adequate and large by Manhattan hotel standards. The beds are (as you'd expect for a Renaissance property) comfortable. The furniture and woodwork is starting to look a little shabby and should be tidied up.
$400 a night is a not unusual rate here - and you do get a pleasant experience - just don't expect this to be up to the standard of other Renaissance properties in a similar city location (e.g. Chicago downtown).