Life - This is the first actually useful Sealstone on this list. Stick it on a fast healer who doesn't get early revival (or those with power/resources to spare - hi Mint!), and then move it around to someone who gets crappy/situational late healing, like... Uh... WAo Jack? S4 Ted? Who else has crappy/situational late healing?
Speed? - Another very nice Sealstone. It's main use is for either Buffers, or Tanks that have overkill, OVERKILL MT damage but probably see a turn once an enemy has seen four. I'm almost thinking Jeff would like this later on in the dungeon (going on the IF-statement that his speed would be changed enough for the formula for Big/Multi Bottle Rocket accuracy formulas).
Resourceless - Ah, the Blitzing Stone of the Gods. Yuri1 loves you forever once Seraphic Radiance opens up. Sasarai loves you early... Riddel or Serge for the mid-game? Certainly a very situational stone, but by all means powerful when used with the right team.
Multitarget - Ah, the center of the most recent debacle. Halves the power of everything, but hits the whole party. Also not immune to buffs from other characters to get around this downside!... Yeah. I'd almost want to say that in addition to its current penalties, that buffs wouldn't affect the holder at all, even though the user can be debuffed (and have those debuffs healed). Would that help the controversy, maybe?
Violent Burst Law - The only games that can arguably use this... Actually benefit from draining those bars quickly. Raquel? Maxed out at 4 shots of Intrude, where she'd normally get MUCH higher further on. Also makes Moonlight -> Intrude chain for Physical charging useless. Cloud? One shot, then no real scary damage anymore. Tidus won't get multiple Overdrives a floor, Yuna... Really doesn't care anyway... In fact, I'm pretty sure that the only character that completely benefits from this is Lilka, and that's if she agrees to never die (unless VBL would keep her from losing all her FP upon death) and to never use Mystic (the only of her Force Abilities worth using anyway).
Status Symbol Law - Positive? Never worry about enemy status whores! Negative? Die anyway, since you're now slower and frailer! Yeah.
Love Love: So, what happens with genderless targets, like Ditto and Worker 8, or generics that can actually have different genders in-game, like FFT Ninja, Pikachu, or even the FF5 Blue Mage (Having Lenna/Faris/Krile vs. Galuf/Bartz?)?
Elemental Advance Sealstone: This is one of those that's really situational. Build a team of characters that can each use two elements (and each picking up the two SAME elements makes this harder). Not only that, though, but enemies can also either punish you for it, or mess up your strategies. This Sealstone suffers from the fact that if you focus on one element, you make yourself FAR more likely to get walled/messed up.
Vantage Effect Sealstone: I... Don't even know how this is used, much less how it can be useful. There's not a lot of counter abilities - counter-attacks, yes, but not counter abilities.
Firefly: So... Just waiting for the proper reapplication for this Sealstone.
There, anything I missed?