Demo or not... drastic changes are needed.
I am a huge old-school Metroid fan. I'd normally eat up anything with the classic Metroid elements in it and call it great even if it was less-than-great in reality. This one could make it to that level - but it needs more than just a face-lift from the demo version. It needs to look less like Berzerk (yes, the Atari game)! The feel isn't so great, either. I guess it might be an improvement over mouse controls (I did not play the first one) but it still feels rather stale. This has puzzler potential I'd like to see explored. This could get much better - but way WAAAAY more work needs to be done to get it there.