So, I judged the tracks based on the idea that GX is trying to bring some of the sensory experiences of gaming into the web browsing space. I also prioritised the more ambient tracks, as we're really looking for music you can read and write too.
Some of the tracks - especially Track J - seem to have forgotten these two factors when trying to capture what GX is about, and whilst Track J is certainly the one that I would have picked as "the best piece of music" I think it failed to meet the basic criteria that you'd want from ambient background music. It draws too much attention to itself. I found myself becoming invested in the music, rather than it encouraging my investment in the browsing experience.
The tracks I think met the bar here were Tracks B, D and F. Sadly, Track B doesn't add anything meaningful to the existing background music. It seems very much to be an extension of what already works, and whilst it certainly achieves that with confidence... it's for this reason I didn't vote for it. Comparatively, Tracks D and F really are offering something new, something different to the base background music. Honestly, the only thing that drew me away from F and towards D was the use of minor off-key chord changes that really threw off the ambience the rest of the track is going for. It draws you into the track too overtly, in a similar way to how Track J works. Without these minor off-key chord changes, it would have got my vote without a doubt.
In the end, Track D got my vote. It struck all the right chords for me, and offered a peaceful and understated composition that I could easily sit and listen to for hours while I type or read without it offering needless distraction or suffering from the composers need to draw attention to themselves. A good composer is one who composes to the brief, and I feel that Track D did this flawlessly where the others did not.