Favorite brunch/lunch place in SOMA...
SOMA is not usually where I hang at brunch time so my advice it limited. If you are coming from Limn, Momo's would be a good bet. I've been to Delancey Street Cafe a couple of times and enjoyed it.
Getting further away....
Kelly's Mission Rock is good, but since they remodeled - well, its just not the same.
Universal Cafe is quite good, really fresh, clean food.
Buzz 9 - I've heard good things about but have not been yet.
If the weather is nice, and we want to be on the water, we go to Jelly's - the food is not fancy, but its on the water, has a patio and its never busy. I think of it as The Ramp with better food but without the crowd.