Having been a Yazoo collector for years, this box set sadly doesn't feature any tracks or remixes that I don't already own on cd. The biggest omission to me is the wonderful "Get Set" they recorded for a BBC show. With all the BBC performances featured on In Your Room, I was extremely disappointed to see that Get Set had not been included.
Having said that, I was very excited about hearing both Yazoo albums remixed in 5.1 stereo. These surround versions are very different in some places to the stereo mixes, to a point where whole notes are missing, parts are mixed into the background to being almost in-audible, and other parts that were background noises before, now become lead sounds. In some cases it works out beautifully, in others it is very annoying to find your favourite sound practically gone from the mix (the rhythmic, crispy synth sound right before "Hey baby!" in Walk Away From Love!). Also listen to the intro of Walk Away From Love; the drums and bass crash in quite crudely, where originally it builds up very smoothly.
Then, there is the overall extreme compression of the 5.1 mixes, making them sound extremely "in your face". This is especially obvious on Vince's voice in I Before E Except After C, making it almost uncomfortable to listen to.
So, are these mixes an improvement? I think they are a very interesting re-interpretation, and offer insight into the tracks, giving you the chance to hear certain parts for the first time, Alison's voice sounding very clear and crisp. You'll discover bits you didn't realize were in there (even extra dialogue in Ode To Boy, right after "that I'm in awe of his despair"!)
All in all, still a great buy, even for the avid collector like me.