My comments (long... very long)
I am not a professional reviewer, but I will add my 2 cents, mostly from the role-playing side.
Presentation:
The book is well-constructed and feels as sturdy as other recent WotC books. Interior art is interesting, and the pairing of photos of the finished minis with the original concept sketches for them is a nice motif. The RPG material is set off in its own chapters, making most of it easy to find regardless of whether you are using the minis rules or not.
Content:
Base Classes
Four new Base classes are presented, but only 1 feels right to me. The Marshall fills a niche (the Captain or Squad Leader role) that my players and I have sometimes tripped over. The mechanics seem Ok, but it will require some playtesting to be certain. Of the others, they generally seem over-simplified. The Healer pretty much ONLY heals; the Warmage is an armored Sorcerer whose spells are ALL (and ONLY) the Ka-Boom combat ones.
The Favored Soul ... well, there are already some who feel that the Cleric is over-powered; now, there's a new top dog: the Favored Soul. The FS gets the Cleric armor & weapon proficiencies, BAB, d8 HD, and 2 skill points/level; all saves are Good; and casts much like a Sorcerer. Their limitations are two-fold: 1) they need both Charisma and Wisdom for their spells, and 2) their spell selection is limited to a small number "known" from the Cleric spell list. However, over the course of their career, they get Weapon Focus, Weapon Specialization, Resistance to 3 energies, Damage Reduction, and Wings. They do not get to Turn Undead, nor do they get access to Domains. All-in-all, I think the balance still comes out tilted toward the Favoerd Soul (as compared to the Cleric).
Healer and Warmage have their own spell lists, which severely limit the abilities of the Healer while focusing those of the Warmage.
The Healer is allowed only Light armor, and loses his/her powers when using Medium or Heavy armor. The Healer has Wizard BAB, d8 HD, 4 skill points/level, Fort and Will are good saves, and all class features are healing oriented. Many class features are 1/day uses of 'Remove X' (Blindness, Disease, etc.). The Healer, being a dedicated walking first-aid-kit, seems better suited to a role as a Cohort than as a PC.
The Warmage will appeal to those who have long wanted to see Mages take a more front-line approach to combats. They learn to negate the arcane spell failure chance of Light armor and shield, and later can do the same with Medium armor. The Warmage has Wizard BAB, d6 HD, 2 skill points / level. Warmages cast like Sorcerers ... Charisma based, spontaneous casting. However, there is no mention of a limit to spells known; presumably, because the spell list is so small, all Warmages learn all Warmage spells as soon as they are able to cast that level of spell. The Warmage, when casting a spell that does hp damage, adds his/her Int bonus to the damage. Over his/her career, the Warmage may learn 4 additional spells not on the Warmage list -- provided it is a Sorcerer/Wizard Evocation spell of a level s/he can use. Additionally, at various levels, the Warmage gains the Sudden versions of some metamagic feats as class features - Empower, Enlarge, Widen, and Maximize. The Warmage does not get a familiar.
In a heavy-combat game, the Warmage outshines the Sorcerer as the arcane battle-platform. The Wizard remains king of versatility, but in a game where that is not a factor, the Warmage becomes a serious alternative. However, I fail to see much value to the Sorcerer in ANY game with the Warmage present, unless Wizards are removed. Both Sorcerer and Warmage cast spontaneously, and have the same spells/day chart. The Warmage works from a smaller list, but it includes all of the hefty combat spells. The Warmage and the Sorcerer get the same number of feats. The Sorcerer has a familiar, but the Warmage can wear armor and shield. The Warmage gains essentially bonus Sudden Metamagic feats that the Sorcerer will not. The Sorcerer's saving grace is that s/he still gets to choose any spells; however, if there are Wizards in the campaign world, that ceases to be as much of an asset.
I am going to skip the Prestige Classes; they seem about as Ok a mix as any other Wizards product.
Spells
Some spells are new, some are revised from Tome & Blood.
The Lesser [Energy] Orb spells are present, and have been revised. I am puzzled, though, at the omission of the [Energy] Orb spells themselves. The existence of a Lesser {something} spell implies that there is a non-Lesser version somewhere, but these are not found in the Miniatures Handbook. The originals were 4th level spells; the Miniatures Handbook includes up to 5th level spells, so unless the new versions went up 2 levels, the omission seems odd to me.
The Swift X spells are 1-round-duration versions of some other spells. They seem like a cheesy way to let someone do a cast-move-attack routine. The Swift spells use the Swift action (almost a Free action, but not quite ?!? ), which leaves the caster with both Move and Standard actions still avaialble. Now, correct me if I am wrong, but wasn't the point of revising Haste so you could NOT cast, move, and attack ? Looky, here's "Haste, Swift", which lets you cast a 1-round haste then use its benefits while you move and attack.
The Legion spells are basically "Mass X" spells. We needed another term ?
There are decent nuggets in here. Guided Arrow, which negates partial cover bonuses to a ranged attack, is a rather nice spell. Bigby's Slapping Hand is ... amusing.
Feats
As mentioned, the Sudden X Metamagic feats seem unbalanced. I am not so sure they are 'broken' as much as too easy to get. They are usable once per day, and it does not seem you can take the feat more than once. If they all required that you have the 'Regular' version of the feat as a pre-requisite in addition to the ones listed, I think they would be fine.
Other feats... well, your mileage may vary. Double-Hit allows you to use both your primary and secondary weapons for Attacks of Opportunity. That adds some value to the Two-Weapon Fighting tree of feats.
Magic Items
There is a discussion going on elsewhere about the merits of the Belt of Magnificence. +6 to all stats, 200,000 gp. Uhm... yeah. That seems... wrong. But, there have been some interesting 'practical' arguments in its favor, countering the 'theoretical' arguments against it. In the end, it serves as a marvelous illustration that DMs should think about what they are giving out -- decide whether it is right for your campaign BEFORE you give it so someone.
On the other hand, the Weapon of Transmutation becomes whatever it material it needs to be to defeat a foe's DR. Uhm... doesn't that make the whole point of the revised DR system moot ? Look, Ma ! A magic sword that changes materials. Now, I'll NEVER have a less-than-optimum weapon for a fight.
Summing Up
Some of the materials feels like the Miniatures authors wrote stuff to deliberately counter what the core RPG revision team was doing. All of it is designed with the Miniatures mindset, of course, but things like the Swift spells and the Weapon of Transmutation seem like they were designed to get around limits that improve the RPG (I like the new DR, for example, and the revised Haste).