Karma is a serene, lovely space with clean studios and loads of props -- including mats, so you don't have to tote yours around all day!\r
As with any busy studio, the class experience depends heavily on the instructor, but I've had only positive experiences with those with whom I've worked. Jesse, the owner, is particularly careful about safe yoga and proper alignment, and Kim and Barrett's classes are excellent as well. I was particuarly surprised to see one poster's comment about an injury sustained at a class at Karma because of the careful attention given to safe practice that I've experienced time and time again here.\r
Their monthly membership packages are a great deal for those who work/learn/live in the Harvard Square area, particularly their student rates.
Pros: Location, convenience, variety of practice styles and class times
Cons: Drop-in rate a bit steep, no "class pack" options (only monthly memberships)