Other:
With DDI, I don't see much need for books that are mostly "rulesy" and a Monster Manual -- chock full of stat blocks -- is on that list. I much prefer using DDI to pull my monsters from, because then I can reskin, copy/paste, and do all that junk.
Now, I'll definitely thumb through the book, to check out some of the art and some of the "fluffier" stuff that they add, but unless there's something amazing in there that I need to reference time and time again, I doubt I'll pick up the book. Not saying it won't happen, but that it's not likely.
If Monster Manuals come with "something else" beyond monster stat blocks and Knowledge check results, then sign me up. I don't know what that something else is, though. Some thoughts:
- really good, in-depth (but preferably not LONG) ecology info
- good lair maps
- monster and encounter design tips, tricks and articles
- stuff I can't find on DDI (maybe new lists of traps, poisons, diseases along with fluff text, in addition to [and hopefully with thematic ties to] the monsters appearing)
- story ideas/essays featuring info on the specific monsters
- playtest notes?
- alternate designs of specific abilities (rather than just alternate takes on a monster; kind of like the add-on abilities that I believe show up for existing undead in Open Grave)
A standalone adventure with monsters from that manual appearing might be neat. Or campaign ideas.
Not really sure though what it would take. DDI is just way more my style, because I'm cool with doing must of the story/setting stuff on my own, and I don't need to reference pictures often.