This track really sounds nice, there is an excellent atmospheric feel to it, whilst it retains a trancy flow. I'm excited to hear the final version already.
The percussion is simple, yet extremely appealing.
Maybe you could work a nice break out of the high synth melody, rearranging it a bit.
A little light glitchwork would really make a nice build, I like the light bass synth in my left ear, kinda 303ish, with a slap bass feel to it.
You should definitely work something into the piano line you have there, give the song some progression, although I like how it is tying things together.
As for the strings, maybe switch from the whole note measure by measure progression to one in half notes, or sustain portions of the chord all the way through the measure, but switch out notes on the chords halfway through the measure.
Those are all the suggestions I can think of the moment, good luck with the final song!