I'm an old-school Mega Man fan, too. (Started with Mega Man 2 and then went back to play Mega Man 1 before Mega Man 3 came out.) I have gotten pretty concerned about Mega Man 11 in recent months. I can't play the Demo since it's not on Steam, but from what I've seen and read, it doesn't come across as a confident next-gen 2D Mega Man. The Double Gear system seems to have been put in there to make the concept of Mega Man more accessible to a general audience, which is understandable, but then I hear they baked it into the level design fairly heavily, making it less optional than I had expected. As was said here, I think it might take away from using Robot Masters' weapons. They've had upgrade parts you could buy from Auto or Dr. Light for a while in the series, so I'm a little surprised the Double Gear wasn't put into something like that. The way each boss is like two bosses in one kind of makes me feel like I won't get a good feel for a boss' standard identity. But overall, it just looks sort of bland. It doesn't look overwhelmingly like a next-gen Mega Man game. I really liked Mega Man 7, and this doesn't feel like the kind of jump we saw from the NES to SNES. A lot of the backgrounds and foregrounds look too simple or washed out. The game doesn't "pop." I'm not sure it's much better visually than Mighty No.9 on the whole. It may be more consistent, but in terms of overall visual impact, not so much from what I've seen so far.
Mighty No.9 was rough around the edges (some spots of slowdown and unpolished graphical effects/models) and was part of a Kickstarter fiasco, but Mighty No.9 was actually a really fun game once one got used to what it was trying to do. (The dash mechanic was even better than X's dash mechanic.) And it took some level design risks with its 3D assets, like objects from the background falling into the foreground and such. I don't know that this new Mega Man is really trying for the wow factor. And after Mega Man 9 and 10 being retro 8-bit titles, I think Mega Man needs some wow factor. Even as a longtime Mega Man fan, I'm not married to it being 8-bit by any means, and feel that I've had more than my share of that style. I want Mega Man to move into the future while still maintaining it's core identity. Mega Man 11 looks like it's more of half-steps, which doesn't separate itself far enough from the experimental Mighty No.9 in my opinion. I mean, Mega Man 11 doesn't really look like it's upped its overall visual impression (aside from rendering) from what we had on the PSP's Powered Up, and that was a while ago.
I'll still pick it up sooner or later, but I'm not exactly hyped.