hi, being a bike courier was one of the best experiences of my life...i didn't do it for a very long time, about 6 months (so technically still a rookie) and it wasn't in nyc...but i met a great bunch of people some of whom i'm still friends with. some days it's the worst job in the world...cold, raining, getting cut up or hit by cars, not getting any good work. but on others..it's awesome, cycling for a living, being outside, checking out the cute receptionists and sharing a great cameradie with other messengers.
yes, faxes and emails have had an impact but there are still plenty of messengers all round the world doing their valuable service as we speak.
couriering got me into fixed riding although i didn't ride fixed at work. but ultimately, don't think you'll get rich quick off it...if you want to make a decent living off it, you have to stick at it so that you climb up from being a rookie and start to get "the gravy". even then you have to work frieking hard...but you will become super fit and have some great stories to tell at the bar.