Ah, I saw this the other day, but didn't have time to watch it! I have now, though. My thoughts:
Overall: I think it would be better if he slowed the tempo down just a tad.
Access, Gestation, Mimiga Town: Beautiful
Balrog's Theme: Lol
Gravity: An interesting take on the song.
Cemetary: I love this song.
On To Grasstown: Hell yes!
Eyes of Flame: Eh... Didn't do it for me. Would probably be better if slower...
Tyrant: Really short, but yeah.
Run!: Now, THIS is a fast song!
Jenka 1: This is my second favourite song, and he does it nice
Jenka 2: Ugh, I can't even hear the notes...
Labyrinth Fight: ... in stark contrast to this, which is made of pure awesome
Geothermal: Another beautiful song which he did not ruin by making really fast.
Oppression: It's hard to mess this song up, since it's basically a mashup in the original, but this is very nice!
Moonsong: Again, just beautiful. This song was designed for piano.
Hero's End: A strangely eerie song... just as it should be.
Cave Story: Alas, too fast. Other than that, it's well played, other than a few missed notes.
Last Cave: This... this has a different feel than the original. But, that's not necessarily a bad thing.
Balcony: The calm before the storm...
Charge: f*** YES.
Zombie: A jarring piece, but that's a good thing in this case.
Last Battle: A fitting rendition of this awesome song.
Break Down: A haunting song, and he captures it nicely.
Running Hell: Yes yes yes!
No love for: Mischievous Robot, Pulse, Safety, Meltdown 2, Living Waterway, Quiet, The Way Back Home, Toroko's Theme.