I bought the 150 from KEH, but immediately changed my mind. I only bought it because the price went below $400. I'm sort of glad it made it to me, just so that I could handle it. The 7 bodies are so light and relatively cheap in terms of construction materials, but the lenses are just the opposite. They're beautiful, and none more so than the 150. I returned the copy, but I came away knowing that I don't think I would want one (unless it was free or almost so).
The closest you can get to to a 50 (on 35mm) on the 7 is the 80, and it's more like a 40. I actually think it's the closest to being "just right," at least for me. I photograph almost nothing but people with my 7, mainly portraits, and the 80 works great for me for that purpose. When I had the 65 and was using it regularly, I also didn't think the 80 would have enough space for me, but it does, particularly now. Also, the lighter weight is a plus. It balances well with the body and that's part of why I prefer working with the 7 more than anything else.