I watched Planet Wisp footage and it IS difficult looking as a final stage should be, but not Eggmanland difficult. Each act takes roughly 10 minutes and difficulty is in line with the final Sonic Colors stages. Tough bits, but frequent checkpoints so if you have a few lives you'll make it through your first time. The guy I saw playing died a few times, but he completed both stages.
Well I never found the Sonic sections of Eggmanland super hard, it was the werehog that made it so hard for me.
My friend described Planet Wisp difficulty as a mix between adabat and eggmanland. I'm not saying hes right, but seeing people complain that it looks too hard or "cheap" makes me think its harder then Colors. I found Colors really easy until I got to stupid terminal velocity, which was hard because of the stupid side-step controls.
Won't be too much longer until I get to see for myself... 3 more days! XD
I've listened to some music, trying to hold off on most of it XD. I know if I hold off until I get the game I'll thank myself. I really wish the game never broke street date XD, so many surprises ruined.
