1) FDR Drive/E River path at night - crrrrap! Hexagonal faux cobblestone for most of the way, which makes for a very bumpy ride. There is one really nice stretch in the upper 70s - I had forgotten that East End Avenue existed - where the lights are in working order and it's (relatively) peaceful. Mind you, you're riding alongside four lanes of constant, fast-moving traffic, but you get a wonderful view of some truly extravagant apartments. Then you get to the poorly lit, rat-infested part where, at any moment, it seems someone might spring out of the bushes and rip you off your bicycle. At around 63rd St, everything grinds to a halt because of construction.
When I took this route on Thursday evening, I transferred to the street for the rest of the ride home and got to experience my favorite bike ride from childhood. I remember thinking the hill just before the Queensboro Bridge was huge when I was a child and, of course, it's nothing as an adult (and certainly insignificant when compared with most of San Francisco's terrain).
2) The Greenway (path alongside and under Route 9/West Side Highway) at dusk - lovely. I entered the path in the upper 40s and somewhere around 79th St. it seemed to persuade me into Riverside Park, which then spewed me onto Riverside Dr. at around 95th/96th St. All in all a lovely ride - much quieter than its east side counterpart.
3) The Greenway at night - impossible to find and has a treacherous track record. I simply couldn't get to it and had various false starts down some unsavory paths in Riverside Park and at the mouths of some uninviting tunnels so I gave up. Also, three people people have been killed by motorists while riding on or en route to the greenway (all, I think, below 57th St.) in the last year.
And, in other news, 52nd St. has a ton of potholes.