The new hair adds a ton of polys to the render. Each strand is set at 20 polygons as the default. With just one 'clump' of 1000 strands, you've included 20,000 polygons to the render. Add any refection and the overhead goes up drastically. One curious thing I noted was that, with FireFly, small test renders can actually take much longer then full size renders. I think it has to do with the bucket size setting but am still investigating that one.