I just got back from the Cast preview of Taste of Africa. I enjoyed myself, and I think it'll be successful. The best way to describe it is basically as a mini Food and Wine festival.
The party starts as the Jammin' Jungle Parade comes back into Harambe after traveling around the Tree of Life. As it passes the Dawa Bar, the DJ above one of the buildings (actually, the restrooms, IIRC) announces that the party has begun, and merchants with various carts step into the parade route and follow Mickey's float. Soon after, they're joined by the stiltwalkers from the parade carrying banners along with the party patrols on bikes. As they start to clear out, the ropes from the parade are rolled up, and the DJ gets started and continues throughout the night.
Each of the existing food venues (with the exception of Tusker House) now starts serving Food and Wine-sized portions of African food. A couple additional stands were set up, notably one across from Tamu Tamu near the river. Most that I saw and tried seem very similar, or perhaps identical, to dishes currently served in Boma and Sanaa (I see this as a good thing). Prices were in the $2.50-$4.00 range, and in several cases portions were pretty large for the money--good value and good quality. There was a wine tasting (and non-alcoholic tropical juice tasting) area set up in the courtyard behind Tamu Tamu.
In addition to the food and DJ, there was a band set up in front of Tusker House, and Animal Programs was doing some sort of presentation at the Harambe School. There was also a wood carver in front of Mombassa Marketplace. The Africa Cultural Reps were wandering around and talking to Guests.
There were only a few things I wasn't enamoured of. I thought the DJ was a little too loud, though not to the point of obnoxiousness. The lines for food were also very long, though I think that may have been a function of it being the first night, and the food being free, thus in much higher demand than normal.
So, in conclusion, if you have the opportunity, definitely check this out.