Hmm. I've had awhile to think about this, and here's my thoughts:
The Good:
Disc Four will contain Trailers AND TV Spots! - I'm a trailer whore, so it's expected for me to be giddy over these. I hope they include some of the foreign versions too.
"Creating the World of Harry Potter" is about ALL the movies - oh yeah, who called it?

Now I'm really hoping we'll get a "Trailers" documentary!
Original Bonus Features are intact - while it doesn't mean much for me regarding some of the early sets (honestly, I only ever re-watch "Capturing the Stone" on
Sorcerer's Stone and never bothered with the rest after my first viewing of them), it bodes well for
Goblet of Fire, which I feel has the strongest supplements of all five films out now. So I'd hate for any of it to be left out of the new sets.
Digital Copy does not count towards the "Four Disc" of the Ultimate Editions - rather, it's an expendable Disc Five that one could easily junk and just insert the soundtrack CD or something.
In-Movie Experience & Maximum Movie Mode - since we can't have straightforward two-hour documentaries for each movie, this is the next best thing. And as someone who is more of a special features fanatic than a technical fanatic, this is a big selling point for anyone who wants to jump to Blu.
The Bad:
Extended Editions are on another disc (for the DVD, at least) - Warner just doesn't like seamless branching, do they? I think beyond the big honkin' boxset for
Blade Runner (for the third disc, which features the other 3 versions of the film via branching), they've never really done seamless branching for any of their movies. Off the top of my heads, Warner movies with separate discs (and/or separate releases) for alternate versions of a film:
Superman: The Movie,
I Am Legend,
Strangers on a Train,
Alexander, and
Pat Garrett and Billy the Kid. The last one is understandable, though, as a comparison of the two shows that two different source elements are used, so branching would make the film look different every time something was branched out. But still, Warner never really likes to seamless-branch anything. Unlike Fox, who's had successful branching versions for stuff like the
Alien Quadrilogy and
The Abyss.
ADDITIONAL Deleted Scenes for Sorcerer's Stone - Warner, if you're gonna go all out for the Extended Edition, don't make us watch more deleted scenes on the fourth disc. Just put them back into the film. But if it's an artistic decision by Columbus (maybe he feels the extended-with-seven-minutes edition was enough), then I respect that. But really...that's like adding a 30-second scene to a TV show and calling it "Extended Edition". No...wait, that's Buena Vista Home Entertainment and some of their Touchstone TV season sets.
Original Bonus Features are intact - this is both good and bad because while I'm glad that everything from
Goblet of Fire gets carried over, there's really a lot of useless fluff that will be carried over too. For example, "The Hidden Secrets of Harry Potter" from
Order of the Phoenix was a joke of a "documentary" (really, just a recap of the books and a "what do you think will happen next?") and I know it has some historical purposes when you consider when it was made, but really, there's a lot more stuff they could do with that 45 minutes of time if that documentary was dropped.
No film-specific documentaries - I know I already said I was glad to have stuff like IME and MMM for the Blu-Rays, but really, can't they throw a bone to the still-faithful-to-DVD crowd by at least repurposing some of that into film-specific documentaries just for the DVD? Heck, the fourth disc for the DVD can be a one-hour documentary about the movie, a one-hour "Creating the World of Harry Potter" documentary, the fluffy HBO First Looks and other mainly-for-publicity TV specials, and the trailers/tv spots. Then on the Blu-Ray, there's already IME and MMM so the one-hour documentary wouldn't be necessary (though maybe it can be an option to watch instead of watching the IME/MMM stuff with the film). Everyone gets something and DVD won't be as deprived as it already is.
albert