In reality, whether you end up staying in Nairobi because of flight timings, or because you choose to break your journey, it's well worth opening your eyes to the spectacle that is modern Nairobi and there is plenty to recommend it for a short visit. Nairobi is a colourful, messy, noisy city, which is, above all, quite unlike what we in the west have come to expect cities to be about.
Consequently there is something mesmerising in the chaotic sprawl of the place; Maasai cattle mix with pickups staggering under truly massive loads. Stalls selling fruit and vegetables line the streets and there's evidence of myriad small business activities at every junction - basket weaving, lawnmower servicing, log deliveries. This is people watching on a grand scale. The modern side of Nairobi has developed a great deal over the last ten years and there are now a few clean, neat shopping malls, South African-style cinema complexes and a variety of really great restaurants, from authentic Indian to sushi and Italian.
Surrounding Nairobi City itself is a varied landscape. To the west, the landscape is arid with wide grassy plains and acacia scrub. To the south, the Ngong Hills mark the boundary to the Great Rift Valley, providing a dramatic vantage point and some interesting scenery. To the north and west, the land slopes steadily up to an altitude of 7,000ft where cypress forests and bright green tea farms roll over gentle hills. For those that don't want to stay in town, there are a couple of pleasant places with interesting things to see which you can combine with the attractions of Nairobi itself.
There is a wide variety of opportunities for souvenir shopping; from local markets to refined galleries. The traffic, unfortunately is a real obstacle to any kind of progress so allow some time if you want to really explore.