Firefox Developer Edition is a great and free browser with good tools.
You can download it here: https://www.mozilla.org/en-US/firefox/developer/
Ranked in these QuestionsQuestion Ranking
Pro Ready for work right out-of-the-box
Pro Can be launched alongside Firefox (release version)
Some might find that useless, but that's very practical to dedicate a browser to development.
It's Firefox. It's fast.
Con Lack of support for source maps in blobs
Still a bit buggy support for CSS source maps coming from blobs. The team is working on it though, and the fixes will eventually land in the production code.
Con May be unstable
Since it is a release channel between beta and Nightly, it may be unstable.