If you are in Nairobi and in Karen for another reason, this is a nice place to stop by. Honestly, I would not make this a destination in itself. The factory is very interesting, and the workmanship is beautiful. But, it has the feel of a place that is definitely set up for tourists - an aspect that takes away from the authenticity of its story. However, if beads are your thing, and business-development projects interest you, then visit.
Perhaps what I appreciated most was the gift shop, as there are a ton of different things to buy - special gifts for others. Prices are NOT cheap. But, if you pick up a few small things, you'll still have money for the taxi ride home.