We have eaten at many an Ethiopian restaurant (including a few IN Ethiopia) and Abyssinia is absolutely the top of the list for us. We recommend sitting out in the garden as the weather in Kenya is hard to beat and the atmosphere is very pleasant---plan to spend some time as there is "no hurry in Africa" but know that your food will be freshly prepared and piping hot! All of the dishes are excellent---we especially recommend their doro wot (chicken is prepared in chunks instead of on the bone which we prefer), shiro, tibs (esp the lamb and fish but beware the green chills masquerading as green beans!), ke'y wot, and all the vegetarian dishes are excellent as well. All the dishes are dairy free (made with ghee) and gluten free and they are now making a gluten free injera (not 100% teff but not wheat floor) which we appreciate as a family with those dietary restrictions. We enjoy the level of spiciness but some people may find they prefer the milder dishes like shiro and the veg.
The staff is wonderful, attentive but not hovering. The dishes are all around 600/=KSH which is approximately what you will end up spending per person--again, excellent value! Children are treasured in Africa and our kids love how they are treated by all the staff. We could eat here every day!