Guides, drivers, cooks + fellow travellers
The two halves of the trip were rather different. In Kenya we were the only travellers, so we spent a lot of time talking to Kassim, our guide. His English was completely fluent — and he'd done a university degree and travelled overseas — and we could discuss politics, literature, etc. as well as the wildlife, and I never had to worry about asking difficult questions.
We talked much less to Duncan, who was quite laconic, and Demetrios, who seemed to be too busy smiling to say much!
In Tanzania there were five of us on the trip. The others were Mamie, a New York lawyer who'd just spent a week doing pro bono work with a Care International microfinance program in Malawi, Janet, who was working with an education NGO setting up a program in Arusha, and Brian, a friend who'd come out to join Janet for the week.
On this criteria, Maasai Wanderings scored very highly, at least for us, as it would have been hard to construct a more pleasant group to travel with if we'd tried. (The same tour might not, of course, have been such a good choice for someone who is a partying 18 year old.)
Simon, our guide in Tanzania, had English that was good enough for guiding us, but wasn't fluent and rarely volunteered information (apart from the occasional set-piece speech on e.g. baobab trees). Our driver Muba had better English, if anything, and had worked as a cameraman for television and film crews. And Jackson (Lohai) was good fun too.
The local guides were all friendly and helpful too. (Some of the others didn't hit it off with our host on the last stop in Tanzania, but I think they were just all tired by then.)