Jesus... that lens right there is quite possibly the biggest reason to have that camera, because it's the fastest lens in the entire medium format world.
You can get some really crazy bokeh with that lens, and use it effectively in low light situations. That lens right there is one of the reasons why wedding photographers fucking loved that camera. It's not the best at f1.9 at all - you're going to have corner falloff and a slightly softer image, but the fact that you can go to f1.9 is remarkable. You can achieve the brightest MF viewfinder ever with that lens.
Fuck man... I'd roll with that camera all fucking day. It's light, easy to use, and with effectively a 35 f2.8 and a 50 f1.9, you have a really killer setup. I fucking WISH I could go to f1.9 on my hasselblad 80mm sometimes... but 2.8 is as fast as you're going to get with that.