I ran severe gear 75w110 for quite awhile with absolutely great results and very similar to what you experienced: a great shifting feel and less whine while in gear (which is where I spend most of my time!).
I did switch to extra-S to try it out and it was almost identical, with very light improvement at very low temps.
Unless there is something wrong, leave it in for 15-30k. Get some life out of it.