Things I have learned about the Words of Power system described in the Ultimate Magic playbook.  (More accurately: errors, discrepancies, and problems I have encountered)
The examples on page 165 describe two wordspells.
1) The burst fire blast is a nice example, though for a true copy of the mighty fireball spell, you need to add the lengthy meta word to it.  Then you will have a long range, 20'R burst fireball doing max 10d10 damage.  A sixth level sorcerer could cast this wordspell only once.  Thereafter, it would be limited to medium range.
2) Selected ice blast life leech will not actually give negative levels.  The entire word would be limited to an instantaneous duration, which means the negative levels will come and go in the blink of an eye.  Utterly useless addition to an otherwise fine cold word.
The selected target word's boost effect is completely understandable.  Basically, it adds "mass-" to the wordspell's effects.  Bull Strength, level 2 word.  Mass Bull Strength, level 5 word.  OK, cool.
The healing words exchange healing amount for range.  They do d6 base but add close range instead of touch range.  OK, cool.  That seems fair.  Though they stop at level 4 effect, which seems out of place.  No high level healing or harming effects.
Purify is basically Remove Curse, Remove Disease, and Neutralize Poison all rolled into one spell with the side effect of not being a guaranteed cure, even for a disease or poison.  Though it does remove a permanent negative level without the 1 week rest and 1000gp of diamond dust required.  Oh, and a standard action casting time.  Wow.  Why do clerics now ever used the "refined and evolved" Restoration spell if it sucks so bad compared to the Purify word of power?  Goodbye scrolls of Restoration - hello scrolls of Purify.  Until you need to repair ability drain.  Then a wordcaster is absolutely screwed.
I have already tried to start a thread on the valueless Sense Hidden word.  A see invisible up to 10' (use a meta word to see up to 20'.  But keep in mind that at this point you have a total of 2 meta words per day.) to a spellcaster is utterly useless, especially since you have to end the spell (its duration is concentration, after all) in order to cast another wordspell, but now you can't see your target again so all your other selected target effect words or once again useless.
There are no good dispelling words.  I suppose this could be as designed.  Suppress requires knowing the specific spell effect in the first place, and only on a willing target, and only for a temporary time.  Yes, I know it can be boosted, but remember that at that effect level, the caster will have all of 2 meta words available.
The description of ball lightning runs counter to the description of the selected target word. Try it yourself and see if you can reconcile the opposing descriptions of a boosted selected and the description of multi-targeting ball lightning.  Also, keep in mind that a boosted selected ball lightning is a level 8 word, which is far more limiting than that other level 8 electric word, Thunder Strike.  It doesn't make sense.
Force Bolt is not a magic missile.  First, it's a level 2 effect, and second, it requires a touch attack to hit, and third, it can do more damage at low levels but hits its limit at level 5 (doing 5d4 (5-20), while magic missile is doing 3d4+3 (6-15)).  Mass force bolt is a 5th level spell, and is pretty lame compared to Force Blast, which has no limit to target word.
Servitor words trade a shorter casting time (1 standard action!) for the ability to summon multiples or a lower level monster.  Summon Monster 3, a 3rd level spell, can summon d4+1 1st level monsters, but the equivalent effect word is a boosted servitor 1, which is a 4th level wordspell.
I have seen other mentions of the Decelerate or Accelerate power words.  Yes.  They are pretty costly in any mass kind of form.  The actual Haste spell is level 3, and the closest that Accelerate can do to mimic the effects is as a level 5 twice-boosted wordspell, and that will only allow an extra attack instead of an extra move, no bonus to AC, no bonus to initiative, no bonus to reflex saves.  All for two meta words used in one wordspell.
Teleportation words.  Ugh.  Dimensional Hop yourself as a 3rd level spell.  Hop yourself and others as a 6th level spell, and only within close range (55' at 12th level caster) and only within line of sight.  Yay.  Dimensional Jump yourself as a 5th level spell, but only to a place you have been to before, which is not too bad.  Jump yourself and others as an 8th level spell!
Oh, and only clerics can Dimensional Shift others along with themselves.  Sorcerers/Wizards can only shift themselves, not others; to do so would require a level 10 spell.
How is Ice Wall subject to spell resistance?  OK it's an evocation, it evokes, and usually evoking evokes spell resistance.  But this is a physical wall of ice.  So SR will allow someone to just walk through it, even though the ice has hit points?  Stone Wall is a creation spell, but it also is subject to spell resistance.  So how does that work?
All in all, I do enjoy my wordcasting stormborn sorcerer.  I just wish it didn't feel like a lot of the words and their target resitriction weren't tested at all.  I get the feeling that the entire wordcasting system changed halfway through playtesting and a lot of spell descriptions didn't get updated along the way.
I tried looking for an errata for Ultimate Magic, but I couldn't find one.  I am hoping Words can be cleaned up because they are enjoyable, and I like the faux latin I made up for the Thassilonian words I use with my character.
Please fix them!  Otherwise I will have to fix them with my GM.  So any input is appreciated.