Given the huge drop in tourist traffic in Kenya I can't imagine a lot of increase in NBO flights.
I agree that the lounge is pretty nasty (but with free booze to dull the pain), as is the Swiss airlines plane that flies it

. We got stuck on the runway in NBO for a few hours - the staff were great, but I'm glad that I was up front.
That said, changing in ZRH is great. You can make a short connection, but if you have extra time there between flights it is very easy to head in to town for a couple of hours.
Good luck
Dr. PITUK