I have the R3 disc too. I haven't watched the movie itself yet so I can't comment on the disc change (though I saw ALEXANDER in the cinema).
Transfer seems pretty good to me - very sharp with no visible e.e (on first look anyway). Colours seem a little washed-out at times and a bit too rich at others but this is most likely intentional. R1 transfers usually have the edge on R3 transfers but this one is certainly very good.
The big advantage here is the DTS soundtrack which is rich, full and thunderous - the best of the audio tracks ( the others being DD5.1 and DD2.0). This track is unlikely to be on the Warners release.
As noted, the film continues on Disc 2. Extra features here are a promo doc, an extensive interview gallery (offcuts from the promo by the look of them ) and some B-Roll footage, lasting about twenty minutes (no timings available)- a fairly random collection of Behind The Scenes stuff, presented plainly.
Disc 3 is devoted to FIGHT AGAINST TIME, ostensibly a near-feature length doc on the making of the film. This is NOT, however, your usual stage-by-stage production doc. It's been made by Oliver Stone's son and is a more personal piece. It's all filmed on-set but it's much more about their relationship and about Stone himself. Those looking for a more conventional doc may be disappointed but it's an interesting (if not excellent) addition for Stone-fans.
The set is presented as a gatefold digi-pack, with a pocket that contains four movie-poster repro-postcards in a greaseproof paper envelope (as for MGM's THE GOOD, THE BAD AND THE UGLY S.E) and a numbered certificate -supposedly leather- that's meant to look "ancient" but is, frankly, quite ugly. All this is contained within a very solid box-sleeve. The whole package is nicely designed and completely English-friendly, but it's not particularly lavish in comparison to other R3 limited-edition sets.
Given that the upcoming R1 release will include the FIGHT AGAINST TIME doc and a Stone commentary (not included here), this release only has the DTS track and its early availability to recommend it. I'm happy enough as I'll be picking up the Director's Cut later in the year and this will hopefully be a good supplement to that.