Interesting stuff.
I do like it, and it's got the ambient feel to it. It seems very light yet uplifting which is certainly something that is a plus in this. There were a few things I did pick up on though.
In my opinion, your choice of drums or the way they were placed in the mix was pretty mediocre, as the drums should really be closer to the forefront of the tune in general as that's something that's considered a lot in Drum&Bass / IDM. I'm not saying it's mandatory, but I think you'd have to make it ambient or aggressive, I don't think the middle option is really there in this opinion.
The transitions between sections A>B>A etc etc didn't seem to work that well im my opinion. It's like it suddenly just changed and though it's good to be left guessing what's coming next (and you did time it well) it just didn't seem to flow all that well, though I did like it. An example would be when that porta synth just suddenly went quiet out of nowhere, I wasn't a fan of that transition after the first B section.
One last thing, that lower bass/sawish synth I think was a bit to "chorusy", I guess I like it when a bass swells into something really dirty and hard but then that's my opinion.
I loved the synth in the beginning that went all the way through, really nice use of portamento, top job there. Also loved the IDM section, why wasn't that longer? T_____T I LOVED THAT!!!!
Taking everything into account you did a very good job and I like it a lot, just a few minor changes you can put in there. PM me if you want to enquire about anything I've said in this review.
Anwar Louis ^_^