I just picked up my copy today. The pages are smaller, but that's not really a problem.
I don't know if any monster
categories got dropped, but some monster types were and some were added. (In some cases, many.)
Edit: Homunculi weren't included (they were in MM1), and there's at least some MM2 monsters in there (deathpledged gnolls). YMMV.
The average monster level is lower. (For instance, the lowest-level ogre is level 6, rather than level 8.) IMO this is a plus. In some cases (eg beholders) this is a
big plus. You can have a "full" beholder (rather than a gauth) as a level 9 solo. On occasion, there's a problem: the highest-level dragon is 22nd-level, and doesn't have the ability to strip away fire resistance with its breath weapon. (You could use the MM1 elder red dragon with a few minor changes, I suppose.)
Elites tend to make more sense, especially templated ones. The death knights are actually scary; they're elites, and the blackguard at least gets two attacks (as befits an elite). A lot of "templated" monsters are
not elites; for instance, the various vampire types. On the other hand, some cool monster types are missing. The death knight "blackguard" is a skirmisher, not an anti-paladin, and doesn't have the ability to give undead extra fire damage
The tokens are
very cool, and I have only one complaint. Often monster categories have only one token type to share amongst them. An example would be efreets: the fireblade (level 22 soldier), cinderlord (level 23 artillery) and flamestrider (level 23 skirmisher) all have the same tokens. So if you wanted to set up a typical 23rd-level encounter of 1 fireblade, 3 flamestriders and 1 cinderlord... good luck distinguishing them. Lower-level monsters like duergar, hobgoblins and gnolls run into the same problem.
