I think this is a highlight in DT's career for many reasons. For once, I think it's something like they've never done before and very out of their comfort zone. Their songs fill very full because they have many tonal changes, arrangements, notes, etc. Space Dye Vest is everything a classic DT song is not, and that puts it on a category of its own. I know this is a Kevin Moore song considering he brought it to the band just like John Petrucci has brought several finished songs (Beneath the Surface, Wither, etc.), but at the end it's a Dream Theater song because he showed it to the other guys to have it make an appearance on the Awake album because he thought it was a good fit, and he was right.
The song is musically very simple, and the highlight lies in the eerie atmosphere, the sound effects, the dreamy voices, everything. I love Dream Theater, and I love Space-Dye Vest because it's everything Dream Theater is not.