This is a seriously awesome office space that any developer looking for the urban lifestyle that NYC offers would be nuts to not want to work at. But Joel, you already have a fantastic reputation and should be able to recruit top talent based on your location, reputation, and because because you employ other smart people. That 500K of your own cash you put into that space depreciates over 39 years. You basically can't write it off until you move! I got stuck with over 200K in our last build-out that I'm still sitting on 3 years later. However if 500K is all you spent in addition to your lease with a standard buildout allowance, you got a great deal.
Like Joel, I bootstrapped a software company to similar size (25 employees). I did a calculation and we spend about 1.4% of our revenue today on 5,000 sqft of office space, but have outgrown it and it's no longer the nice spacious office we started with. 10,000 sqft of space in the best class A space in Western MA will cost about 3% of our 2009 expected revenue, with modest but nice build-out included. Given that this would be our 4th move in 6 years, I tend to be careful about long leases and lease buildouts.
I'd rather invest in paying good salaries, offering the best equipment and a nice (but not extravagant) work environment. Then I can afford to launch new products without being beholden to investors.
I really like the glass walls though...