I appreciate the handbook, having recently come into possession of MoI (by accident no less) and being intrigued by it. The trouble I'm having with it is I cannot understand how an Incarnate or Totemist is actually supposed to vary their role, with essentia (and essentia capacity) being so limited, as well as by the limit in number of melds shaped and the inability to reshape them, except at higher levels. The Incarnate's Incarnum Radiance confounds me, too: how is that supposed to be useful except in a very limited sense?
Additionally, UMD allows you to emulate alignment...is there anything like this for Meldshapers?
The Incarnate is able to cover a number of roles depending on alignment:
LN: Tank. Incarnum Radiance 4/day with a duration of 3+Con mod means you can use it once per encounter. Incarnate Avatar+Incarnate Weapon both stack with the Incarnum Radiance. Optimizing your to-hit value with those three, and you end up with attack rolls in the mid-50's early 60's. Combine this with Robilar's Gambit or Karmic Strike, and it almost manages to make up for your low BAB.
NG: Your AC can hit 70 with no trouble. However, you don't need to invest as much of your feats/items into your AC as everyone else would have to. Because your AC is that high, you can easily sink your cash into UMD-based items like Wands. NG works best with Gestalt (Artificer) because of this. Mage's Spectacles and CC ranks are your best friend here. Grab as many skill boosters as you can, and you can be a mini-caster, even better than the Rogue!
NE: One good side to this is the Teifling sub levels allow you to enter Ur-Priest without multiclassing. If your DM allows you to enter Sapphire Hierarch or makes a variant of it for NE, this can easily be the deal breaker. Otherwise, you end up being a demi-Cleric with UMD, playing a hybrid of the LN and NG (but with lower AC/Attack). Divine Power wands mean you never have to worry about missing, and your damage output will skyrocket.
CN: Skill monkey by near definition. Dissolving Spittle+Greater Psionic Shot+Throat Chakra, and you are set. Think like a Warlock.
Truth is, you don't need max Essentia in all of your soulmelds at all times, just the ones you know will eat into your actions (anything that requires a Standard action for you to use is a good place to invest essentia, as you want that thing to be worth it). Try not to shape too many offense-oriented soulmelds, and you can pretty much leave your Essentia in your Essentia Pool until its your turn. The bonuses from your Soulmelds add up fast, and allow you to exceed the normal limits on skills with a little practice. Remember that the maximum essentia capacity for a 20th level Incarnate is 8 in any Soulmeld you have the Incarnum Focus+Expanded Soulmeld Capacity feat for, so take this into account when shaping your soulmeld.
Totemist is easier to define. You end up playing like a Monk on steroids for everything but damage (I'm comparing this to Dman's Monk builds). The low essentia capacity is offset by the bonuses granted by your soulmelds. At the low levels, you are easily the most powerful non-caster in any party due to your Totem chakra (though 1st level tends to be a bitch).
Typically, you build a Totemist around one or two of his soulmelds and try to pump those two up as much as you can. Girallon Arms, Manticore Belt, Landshark Boots, and a few others make for a good choice (a notable option is Breath Weapon-based Totemists, as they tend to play like a more versatile DFA).
Rule of thumb: Trying to build any meldshaper to be able to cover more than 2 bases will usually flop unless its Gestalt. Its best to take a focus and stick with it from 1-20.
The lack of freedom with your soulmelds is a hindrance if you are focused on a single task. Even at low levels, a Totemist shouldn't have much trouble with their soulmelds/day (1st level is a bitch, again). When you get the Rebind Totem ability, the rest is pure gravy. Incarnates tend to feel the limit for the first 3 levels, but they still play pretty well for that duration. Once they get a few Chakra binds, they start to relax a bit.