I've seen some cyclocross bikes fro decent prices from Performance. They are a little heartier than road bikes without being as cumbersome as a mountain bike.
Edit: Wasn't performance but Nashbar: http://www.nashbar.com/bikes/Product...0_10000_202339. I'd prolly take that price with me to an LBS and see what they can offer.
Roubaix Pro Carbon, Marin 29er Full suspension, 1990's Trek hard-tail
In Manhattan, I'd go with a hybrid bike as well. There's a ton of different options out there and in that price range. Check craigslist first and see if you can get something a little cheaper to get your feet wet, then after a few months on that, you'll know exactly what you are after. Also, if it gets ripped off, you won't be so sad ;-)
I'm not sure what limiting factors you're considering when saying road bikes aren't versatile. I think road bikes are the best for riding on roads, but there is a wide range of road bikes. You can spend thousands on an ultra-lightweight, carbon-fiber beauty witn 23mm tires; and you can spend considerably less on a touring or cyclocross bike that can handle hard knocks, wider tires, big loads, etc.
You can also get a mountain bike that will be rugged and excellent for dirt, but with a simple switch of tires can also be okay (and still rugged) on the road.
What exactly do you want to do with your bike? What road surfaces, what kind of loads, etc.?
Depending if you are going to do a lot of hills or not, a triple instead of a double compact.
No less than Shimano 105 components.
A nice crossbike or a fixed tail MTB with road tires (26" x 1.9"). It can be with a fixed fork or a 80mm (low profile) with lock out. No need to get disc brakes and none of that fancy stuff if you are not competing if you go the MTB route. "Usually" MTBs tend to be pricier do to the components, the fork tends to be where most the money goes. Sometimes is better (money wise) to buy the MTB with fixed fork, and then later swap for suspension of your choice. Because whenever they cut on the price, the fork is junk, but if you want a nice fork everything else is upgraded. So it is very rare to find a nice front suspension fork with basic components when at the end the difference is very minimal.
80's Schwinn Voyageur, '91 Schwinn MP21 MTB, BH Supra300 from Spain, Pacific Dualie Tandem (cheap fun), MyBuild/Lovejoy RoadGoFast, MyBuild/Lovejoy RoadGoAlmostFast. Have owned 2 Treks, '83 Holdsworth Pro (best ever), '85 Paramount
A hybrid, indeed. Check out what's available in shops, then go to www.bikesdirect.com and look at their hybrids. You can get a reasonably decent quality bike for under $450 and still have $50 left in your budget for a shop to assemble/check it over. You'll need a decent (gel) seat, a lock, and a helmet as well.