Pretty much all of it - still as it was when they shut down the blast furnaces 25 years ago - only now completely deserted, save for a small wind farm...
I believe the abandoned facility is now owned by ArcelorMittal, a Luxembourg-based global steel conglomerate - they keep threatening to rehabilitate and develop the site, but that promise hasn't resulted in any activity for at least five years now.
Given the amount of toxic waste buried there and all the infrastructure that traverses the property (RR rights-of-way, high-tension/high-voltage power-grid facilities, etc.), I still think the best use of the site is for a new stadium - right on the water's edge, on a major thoroughfare (Route 5) less than a mile from the NYS Thruway, and a spit from downtown BuffTown.
WNED did a documentary on it (last year, I think)...
Buffalo's Voices of Steel
A couple of other good Bethlehem sites...
The Steel Plant Museum (You get a great perspective of the enormity of the site and its location from the aerial photo on this site's home page)
And, if you're really interested in Buffalo in it's 'heyday' and the city's rich history...
The Buffalonian
Rushing the Growler
Forgotten Buffalo
Buffalo Architecture and History
.