Storyline: 5/10 Mediocre.
Well, I can't exactly call it original, you are in cave story, but you have your friends added too,
and you did it well.
Dialog: 5/10 Mediocre.
It was okay, nuf said.
Level Design: 5/10 Mediocre.
I know I'm starting to sound repetitive, but 5/10 is the most apropriate rating I can find, that and you only edited 2 levels.
Gameplay: 5/10 Mediocre.
It was fun, for what I played of it, but there wasn't much of it. (duh, it's a first demo, and I honestly can't really criticize anyone else's mod short of unplayable, I mean, have you seen MY first demo?
Hopefully not, don't download it, if you want to see my mod at all, download the latest demo, 0.0.0.1 is the worst mod demo in existence.)
Custom Graphics: 7/10 Good.
Nice job, did you make them yourself?
Glitches:
I know you said there were some but I honestly can't find any, including the ones you mentioned.
Improvements: Uhh, more gameplay? that's about it and this is the first demo, so good job.