OK, some more opinions by someone who couldn't write a song unless he had an inbuilt synth track and the chord of C to play with
Machine: love this, very depressing and downbeat but played and sung really well. Feedback ruins it though: had to turn treble to full and bass to zero to get any of it. Also, what's the chorus, as it's not in the lyric?
Overcast: Really liked that. Very spooky/horror/suspense movie vibe, Goes kind of Vangelis near the end. Really cool.
Grtwhtgrvty: Sorry but this sort of thing --- sampling, soundscapes, textures, what have you --- is not my thing. I'm sure it's well done and very clever (you certainly seem to have fans from the comments) but not for me.
YorkeDaddy: Love this too. Very relaxing and sad in a way. You can certainly play a piano. Another favourite.
Plankton: Why bother? Everything this guy touches turns to gold, and this is no exception. A real contender for winner.
Think that's it, of the ones I've listened to. If I've missed anyone out let me know.