The only thing to fear is stability, or too much of it. I have run stretch and sid (testing and unstable currently) and I get a sense that sid is even lighter and more stable in hardware resources. With all the fooling around I do I have yet to see anything break or freeze or do anything unexpected in sid. Stretch is so stable it is boring :) Now Jessie, that is a really unstable system ;b .... even your graphics don't like it.
I have run sid (unstable) for years (a decade? more?), and although there's often little breakages (uh oh, can't install Firefox; wait a day and a half; okay, all better now, it's installed), I can only recall one time (8 years ago? 10?) when the breakage was serious enough that it actually borked my box so I couldn't do anything with it. But even that, as I recall, only had me broken a day or so, as I either manually fixed it, or just reinstalled a fresh sid, or waited until the breakage "fixed itself". The conclusion I have come to after all these years is that for a workstation that doesn't have a mission-critical need for five-9's uptime, sid/unstable is a good solution for staying up-to-date and happy, but it's probably not suitable for a mission-critical box.