Thought I might make some comments too after reading through my copy. From what I have seen so far it is an improvement over MM2 and I like some of the inclusions, but I wish they had added more "3.5 enhancements" of course.
Some things I have seen (might be been mentioned somewhere else but I have not found it mentioned).
Undead/Outsiders don't seem to get Level Adjustments, but any other biped creatures with arms does unless the supposed ECL is above 20.
I like the suggested spell lists for spellcasters but it would of been good to go the extra step and add tactics as well.
Canomorph got me confused, okay they seem to be fiendish lycanthropes and they have monster samples of each type
but where are the templates.
Then I realised there arent any. They just cover the varieties for Hell Hound, Shadow Mastiff and Vorr.
They have level adjustments which conflicts with what I already said. ;-)
Century Worm is CR19, with a swallow whole attack(grapple +54) which will inflict 2d6+9 acid AND 1d8 Con damage very round (Fort DC: 38 to resist).
I don't think so...
I like the comments after some monsters (eg. if you are in Forgotten Realms, if you are playing Oriental Adventures...)
A black Ethergaunt is SO not ECL 20.
I like the choices in spell-like abilities with the Half-Fey, this is should be used more, hopefully we see this in 3.5 with Half-Celestial and Fiend.
Half-Illithid is ok and contains no surprises. Did not inspire my in the least. A bit of a shame, I hoped for more, it is just a rehash of the Mind Flayer, stripped back to a template and slightly crippled.
Half-Troll is weird. It can be applied to Dragons.
Am I a Half-Black Dragon Troll, or a Half-Troll Black Dragon???
I also don't understand how a hill giant breeding with a Troll is even stronger than either Troll or Hill Giant.
(Would have Str 31, Dex 10, Con 25).
Imps have their own section which makes me wonder whether imp will be separated from the Devil entry in MM 3.5.
I could also say I got my money's worth out of this book for the Shadar-Kai. These are what I will base for Unseelie Fae on from now on. I love the Shadow Curse!
Swarm is great, this what I should of done with Vermin Host in CC2.
The Appendixes are a great idea, great to see more than just monster stats. I hope WotC include extra stuff like that in MM 3.5.
regards,
Arawyn