So after playing the demo, my overall thoughts is that it plays like I remembered Sonic 06 but tolerable. My feelings about the demo:
+Loading times are 2 seconds MAX
+Game seems to run decent enough
+Sonic's controls feel tighter but not perfect
+Game just overall feels faster; like a proper follow up to SA1/SA2 Sonic stages
-Sonic's control still isn't 100% OK with me. He sometimes feels still a little sensitive when doing tricky platforming
-Homing attack feels random in what you'll actually home to
-Sonic still isn't as fast as I'd like him to be plus he accelerates rather slowly
-Hints of slowdown here and there but that could just be my rig
Overall, if some improvements are made and support is kept coming, I think this'll turn into something decent for fans of the Sonic Adventure era gameplay