Still to this day the question "is btrfs stable?" cannot be answered with a firm yes. The btrfs faq phrases it the best, nobody is going to one day put a sticker on it that says "STABLE". I began using btrfs about 3 years ago on my laptop, now I also have it on my desktop, and I also plan on reformatting my server too. I can't really say anything about it's performance, because I haven't done any benchmarks, but it definitely doesn't feel any slower than ext4.