First I should note that I use the Steam version, have done a clean re-install, and am working under a brand spanking new test profile. I think that there may be five distinct problems being talked about in this thread (and others); People who dislike the new SAS/Reaction Wheels System purely because they don't understand how it works A Bug or bugs that are causing inconsistency with how the SAS and control systems behave with respect to different craft A Bug or bugs that are causing the SAS and control systems to behave in a 'squishy' manner (bounceback, etc) A Bug or bugs that are causing the SAS and control systems to be nonfunctional resulting in extreme veering etc (Perhaps Steam Related?) A bug or bugs (or working as intended, but very poorly designed behavior) that cause slightly asymmetric craft to veer, and the SAS to fail to correct. I initially experienced #4 on my first pass with 0.21, but a clean re-install and remembering to place electrical systems on my craft has fixed this issue. I continue to experience #'s 2 & 3 at this time; I have done the 'Aeris test,' and done some flying with the Ravenspear and my own jet design and noted extreme inconsistency with the behavior of the SAS, as well as frequent 'spongy' or 'squishy' behavior. I have flown a Kerbal-X to orbit, as well as an 'improves' Kerbal-X with an added RCS system and Inline Advanced Stabilizer. Both exhibit the sponginess in the SAS, and severe under-compensation when trying to correct and hold a heading. I rebuilt this part-for-part based on your images and it flew straight up with no veering or wobbling in the slightest in my current clean-install/new profile. Someone else commented that you're using tailfins; that's incorrect, those are actually 'Standard Canards,' and do in fact articulate and can be used to control a craft. I added some asymmetrical parts to the craft to test for ascent issues, and found none. I do not know for sure how this would behave on-orbit in a maneuver however. I then proceeded to add a small asymmetrically placed engine to see if my SAS could correct; it absolutely could not. Thoughts in total? There are two main issues here; the one that certain users are having where SAS does not function period, and the one many more in total are having where SAS is just behaving poorly, while still technically 'functioning.' I really dislike the way the SAS seems to treat your velocity vector on the navball as your heading, rather than the spot at which you let off the controls; that is my main gripe with it at present. Secondarily, I'm concerned about the orbital issues people have described. I'll be taking my Kerbal-X-i up shortly to test some of these and will get back to you with results momentarily.