I've been here a few times and I have to say that for people who are trying East African food for the first time, it's not bad. However for me, 98.52% of my family is from East Africa, not to mention that I've been there a couple times.. and it's just not the same.
I have to say that the short ribs that are self proclaimed the best ribs in the city, are definitely not, however they aren't bad. The mishkaki (mish-kah-kee) is pretty good, and I personal love ugali (oo-gah-lee). Try the mango lassi as a companion to your meal, especially if its a spicy one.
Post meal, make sure to try the Tanzanian style ice cream and masala tea (aka spiced chai).
Overall I give 3 stars, but maybe that's because I grew up with this food and my idea of authenticity and quality of East African food is extremely high. With that said, Simba Grill does a good job overall.