I've been working with 3 organizations on customizing a 7 night safari. Any feedback on :

Sunvil - out of UK
African Adventures - out of Ft. Lauderdale
Fish Eagle Safaris - out of Houston

The only company I have experience with is Fish Eagle who arranged our trip to South Africa, Botswana and Zimbabwe. It was a great pleasure to work with Bert and I highly recommend the company.

Why don't you consider looking at companies based in South Africa or Botswana. Without exception all these companies are using someone else to put your trip together for you .

There's lots of ideas on this forum

I have used Sunvil for a trip in 2001, they were fine. For my 2004 trip which I started arranging in Jan 2003 I found myself being switched between sales consultants like a hot potato and mistakes were made in responding to my emails. I switched to an operator that I can't say enough good things about - Steppes Africa - also based out of UK - I deal with Illona Seutes, their General Manager. She has invested a huge amount of time, effort and patience in helping me get my trip just right. I am pretty savvy when it comes to money matters but I truly believe that there has been added benefit for me in using an agent and using this agent in particular.
That said, with Sunvil, if you are lucky enough to deal directly with Chris McIntyre, the director, you'll get some superb feedback too.
I also had some early chats with Bert of Fish Eagles though, by his own admission, it didn't make sense for me to book with a US based agent. He's another agent full of information and patience and added value.
For some trips, I agree that using a local operator directly may be best.
If you're looking to book a WS holiday you will have to go via an agency as they don't deal direct with their customers.
I also prefer the stronger legal basis for comeback in case of problems with a UK operator.
Good luck!
Kavey

Thanks everyone for their feedback.