A friend of mine had drill this weekend when we usually play, so we ran the words of power in his absence. I had two players, so one ran a Word sorcerer (Starsoul bloodline), the other ran a normal sorcerer (Orc bloodline).
The first combat was against two 1st level fighters with bows and higher ground. the combat went about as you would expect two sorcerers vs two fighters would go, shots from both sides, lots of misses, not much damage from either sorcerers until the orc blood got feed up with trying to shot at them with magic, and hit them with his axe.
The second combat was the two sorcerers against 8 Kobolds, this combat took forever. They split up on opposite sides of a river to fight 4 kobolds each. The normal sorcerer was able to do area damage, this alone allowed him to take down his 4 faster than the word sorcerer. The normal sorcerer ended up helping the word sorcerer finish them off at the end.
Results: At 1st level the damage of the word sorcerer is far more limited than with the normal sorcerer, 1d4 to one thing as a first level spell. burning hands alone saved the normal sorcerer. Please note, i am providing data not opinion, i'm not suggesting any changes.
Before the next combat, i had the two players level up to 5th. The face off against a tiger CR4 and 4 Kobolds. both players got eaten by the tiger.... the tiger got surprise, grabbed the word sorcerer, and finished him off while the normal sorcerer finished off the Kobolds; a unsurprisingly easy task. the tiger than turned to the normal sorcerer and finished him off just as easy as he did the word sorcerer.
The next combat was against 4 ghoul Kobolds (the mini's where right there and i didn't feel like searching for more). i reduced the ghouls speed to 20 and increased their NA by 1. this combat lasted 1 round, just long enough for the word sorcerer to destroy the ghouls. the normal sorcerer had a chance, he only damage one a little bit.
Results: At 5th level, the word sorcerer gaining new targeting words has made up for 1st. they allow him to do a bunch of damage to a bunch of targets, while still suffering from the same flaws that all sorcerers have at those low levels (lack of a meat shield).
I was the player playing the Orc bloodline normal sorcerer. So far from watching the interactions between the words available for playtesting and the normal allotment of spells (which we just used Corebook and APG spells), I'd say that so far they feel about balanced.
The normal sorcerer has an advantage at 1st and probably through 4th would be my guess. The lack of 2nd level spell slots seems more limiting to the Word caster than the normal one.
However, once that 2nd level slot is open, I think the advantage (in flat out combat, at least) shifts to the Word caster. Their ability to spam damage very carefully to groups starts to kick the normal caster's abilities.
As an example, for area damage spells, one of the better ones for normal casters is Stone Call. 2d6 bludgeoning damage to a 40ft wide cylinder with no save and no spell resistance. However, the Word caster was able to spam fire damage to each enemy (only 4 of them) without endangering my character. They got save for half but it was 5d6, which even halved will be more than the 2d6 on average.
I have a distinct feeling how this will break down is that there will be certain level slots where the Word sorcerer has quite distinct advantages and the other levels will be pretty on par. The question will be "How many of those levels are there?". So far, only testing at either 1st or 5th, I'm seeing a definite advantage to normal sorcerers at 1st, but an advantage to Word sorcerers at 5th in sheer damage output.
As for supplemental spells, that would take some extra looking at.