I'm going to try and stay away from general/personal gripes (eg. lack of monstrous cavalry other than terras/rips)Rule-wise, a lot of these have already been detailed but:
Low toughness on Carnosaur and Troglodon. Considering the new model sizes, and the fact they're supposed to be the central monster of the LM army other than the Steg, and their place in the fluff I expect a little more durability out of them.
Little practical necessity to suit the Troglodon's cost or rather smexy model. The flexibility of the unit is an interesting idea, but the flimsy rules and high points cost make it unjustified for it's worth and it's place as a rare.
Lack of core variety, or rankable units at that. I love Monsters, don't get me wrong, but I don't want to rely on a lumbering target for a powerhouse beyond Temple Guard, and I really want a unit that can help match the variety of other units available to most other armies.
Cold-One Riders are still a tad pricey, but it's mainly the lack of magical banner that irks me (man, the Sun Standard + CoC was amazing). In fact, the only unit other than a BSB that can take a magical banner are the Temple Guard, which seems singificantly less than other armies (I'm looking at you, High Elves!) Ok, that may be close to gripe-land...but I think it's a valid point.
Other comments:
The mysterious, limited edition 'New Art' that appears on p.21 of some copies. Either sloppy editing or subliminal conspiracy, both are unwanted.