To me, the big benefit of Git is private branches. When I'm in development I don't need to build clean, atomic commits or have anything worth pulling. I write commit messages like "savepoint 2013-12-12 do not push". I don't want to think about version control because everything is still dirty.

I don't know if you've looked at the graph of a Git repo where people merge instead of rebase, but even in that view it's nearly impossible to track even the history of master. It's a mess. Rebase builds such cleaner graphs that I would only advocate merge when you have no reason to ever look at the graph view.

For me, almost all of the time, when I'm ready to merge to master I can almost always squash all my work into one or two clean commits. At that point a fastforward is the simplest solution. Merge-only workflows are great for long-lived public branches (if you have an integration and release branch for instance) but they're insane for feature branches.