Fingertips - I'm not too keen on the verses, the chorus is pretty nice. The chord sequence you got works well for the song but I think this would benefit from some drums and a melody on the guitar or maybe piano.
Art - I like the piano. The speaking at is good, maybe a little loud tho. It's pretty good, I like it, it just needs to change a little bit rather than being the same all the way through I think. SOme other instruments would benefit this too. (Like what you bring at the end, but more and at various times through the song)
Revolution - I love the guitar part. The vocals are ok, not as good as on the other tracks. I would love to hear some drums on this.
Weekend - Kinda like art but guitar instead.
I like what you got, you've got a good thing going. I can understand that you may want to be different and use one instrument per song, but I really think you'll be suprised by the changes it will change adding a beat and maybe a piano tune or something.
Keep it up.