I've only spent 1 day looking at upsource but this immediately jumped out at me: Can side-by-side be the default always? Having to click to get a side-by-side view seems like a show stopper to me. We are just so used to the side-by-side view here that I can't see forcing people to look at inline by default. For a single changelist we really want a single page that shows side-by-side view of each file one after the other. Swarm does this. We are considering jumping from swarm to upsource for admistration reasons but I think this would be a show stopper.