A first read through gave me an odd impression of the system. It being piecemeal (not necessarily a bad thing) gives those who use it added versatility over regular casters at the cost of... versatility.
Consider that traditional spellcasters have a huge selection of pre-existing spells from which they can choose. To become a wordcaster however, they have to give up access to all those spells to instead choose from a narrower selection of combinable words. I understand that there will eventually be more words to choose from, but it seems doubtful that there can ever be enough words to replicate all of the effects possible with traditional spells. So, sure, a wordcaster has added versatility with those word/effects with which he's familiar, but at the expense of all the niche effects provided by traditional spells.
So one type of versatility is, in effect, traded for another kind of versatility. That to say I'm not yet sold on the notion. I'm curious if anyone feels the way I do.
They're not fully rid of the normal spells because they can use spell trigger(like wands) and spell completion(scrolls) items normally. It's not as harsh as it sounds.
As far as effects go, most straightforward buffs/damage dealers/debuffs can easily be put under the words, effectively becoming two or three spells at once due to the meta/target matching. The only thing I see that could keep it from overcoming the normal spells' variety is a lack of investiment in it (namely, never touching it again after Ultimate Magic is released).
Consider that traditional spellcasters have a huge selection of pre-existing spells from which they can choose. To become a wordcaster however, they have to give up access to all those spells to instead choose from a narrower selection of combinable words. I understand that there will eventually be more words to choose from, but it seems doubtful that there can ever be enough words to replicate all of the effects possible with traditional spells. So, sure, a wordcaster has added versatility with those word/effects with which he's familiar, but at the expense of all the niche effects provided by traditional spells.
I agree that wordcasting seems like kind of a raw deal for a cleric, say, who has a huge number of spells known, plus the additional ability to cast some spells spontaneously. But for a sorcerer, it may well be that the number of useful effects he can create with words known + metamagic is more the number of useful effects he can create with spells known + metamagic.
This all hinges on the "to be determined" additional words that Jason has said will be in the final product. If there are many more useful words added, then the wordcasting sorcerer may have a sizeable advantage. But if there are only one or two new words added, it'll end up being a bit of a dud.
For now, I'm a bit skeptical since there were several comments along the lines of "there will be more X in the final version of the Advanced Player's Guide" (e.g. symbol spells for the Lore oracle to use, or cold spells for the Waves oracle to use) that ended up sounding a bit hollow.
For clerics, don't be surprised if they pray for words each day, rather than learn a set number of words.