I'd suggest looking at it two ways.
Firstly- most projections are that, nationwide, prices should retreat to the levels during 2003. New York has tended to be insulated from national trends, however, the fabric of our economy has just absorbed the biggest hit in our lifetimes. In NYC, we're going to see deterioration over the next 6-18 months. It's hard to say how much. The expectations are that appreciation will be very marginal in the following 2 years (2010+). Certain neighborhoods of Manhattan and Brooklyn will be insulated from deterioration. Hard to say if Clinton Hill is one of them.
Secondly, long-term, most economists believe that the "right" home price should be around 15 X annual rent (on a comparative property). Personally, as this is the historical average, I am using this as a guideline for a purchase of my own.
You didn't specifically ask this, but your investment decision should consider how much you're putting down, and the impact on price deterioration. I'd recommend trying a "Rent vs. Buy" calculator, and assume no price appreciation (to be conservative). If this comes up positive, and you love the place, pull the trigger.