I've hunted with two so far, HHK in Zim and Tanzania Gametracker Safaris in Tanzania. I would highly recommend either, but hunting in the two countries is not very similar with different needs by the hunter and responsibilities by the safari company.
I'm looking forward to hunting with Luke Samaras Safaris in Tanzania in a few months. While I have no experience with them yet in the field, to date they have not offered the over-the-top customer service that TGT provided prior to my hunt my hunt with them. We'll just have to see how things work out after spending a few weeks with them in the Selous.