Wazima is the best place in SF for good, cheap Ethiopian food in large quantities. I always get the all-you-can-eat vegan platter and my favorites are the yellow split peas and the spicy red lentils. Their injera is also really light and fluffy.
The service, however, is really poor. They drop off your food and never return, presumably because they don't want you to keep asking for refills. Last night, my friend took our plate back up to the front and refilled it in the kitchen herself then brought it back with the pitcher of water.
That said, I come here every time I'm in town and probably will continue coming here just because the food is so good, so cheap, and so plentiful.