I've converted a few 2x7 and 2x8 Shimano equiped bikes to flat bars and Acera brifters. This is mrs non-fixie's favorite ride, which - until yesterday - had a 2x7 Shimano 105 drivetrain and the aforementioned Acera's. It now has a 105 triple up front for taking on the hills in Tuscany later this year. In this case I changed the derailleurs to Deore to handle the chain slack and the triple shifting better though. The Acera's are pretty cheap, but work well so far.