LOL at above. Don't lose the Smash Ball in the process... =P
FSes are designed to be cheap, in order to make the game more accessible to others. =P Or so we assume.
I tend to prefer hit-or-miss ones and some transformation ones...
Let me go through each character's as relevant (combining those with similar FSs):
Mario: Big deal, stay above/under/behind the Finale... =P
Luigi: This is a tactical one that I don't mind, but it's useless outside the negative radius (I think...)
Peach: The putting others to sleep doesn't work half the time =P And with Peach as a defensive character, the option to eat or beat (up) is rather lousy...
Bowser: OK, but unwieldy.
DK: Useless outside a certain radius, but pretty funky otherwise...
Diddy: I don't recall whether this was true or relative flight control, but not my favorite transformation - it's tough to angle the popguns.
Yoshi: Decent, but the single fireballs get cheap. =P
Wario: Alright except for the rocket-speed Wario Bike. I love the aerial rave ability Wario has as Wario-Man.
Link/Toon Link: Dislike it a little since the opponent only needs to be in line...
Zelda/Sheik: Similar to Triforce Slash, 'cept it's more useful with the linear multihit
Ganondorf: Awe-inspiring but much disliked. It doesn't even qualify as a transformation... =P
Samus: Rarely used it, and like Mario Finale, can be evaded. The angling doesn't help it too much...
ZSS: Almost useless (especially as I prefer ZSS over Samus), but get in your opponent's face and it does... something.
Pit: If more Centurions were employed/they were tougher than they are, this would be broken =P
Ice Climbers: Apart from making the stage unbearably obscured and the freezing, didn't like this.
ROB: This is just a burst ability of active Diffusion Lasers. Nothing special... if it weren't for the fact that ROB becomes impossible to pressure in rush battles or long range >_>
Kirby: Silly, and ineffective sans items.
Meta Knight: Decent, but the cape having only narrow horizontal reach is annoying.
Dedede: Silly but at least better than Kirby's >_> The occasional Gordo is good but rarely is effective except when the foe is caught in the army
Olimar: Boring, but definitely throws people off without a frame of reference for the stage
Fox/Falco/Wolf: Fun to use but only the barrel roll and Landmaster landing (or crashing =P) are effective for me.
Cpt Falcon: Cinematics =/= Smash Bros. And the hit/miss here is HORRIBLE.
Pikachu: Unwieldy but ignores stage barriers. Note that Pika will oscillate around a fixed point if you don't move it (Ctrl Stick or other motion input).
PKMN Trainer: Again, dodge behind. The three angle does make it better than Finale or Zero Laser...
Lucario: Better than Zero Laser since it's from above. And I have to try Snowy's hissatsu skill =P
Jigglypuff: Useless in large stages, but funny and does damage just as Jiggly deflates. That is, if anyone's near >_>
Marth: The ultimate hit or miss =P OK, but not stage friendly at all.
Ike: Perhaps my fave. The range is appropriate and the animation is Ike worthy.
Ness/Lucas: Apart from the angles at which the Starstorm emerges from, much the same, and rather effective in many types of stages, since a single meteor can do a lot on its own (and you often only get hit by a few)
G+W: Apart from the suicide danger and platform blockage, alright.
Sonic: I'll show you!! =P Too fast IMO, but definitely cheap if used at an opportune moment. Thankfully he's blocked by the stage...
Snake: My second fave. Aim and shoot tactically. So much better then watching other fall asleep and decide what to do next. =P
My verdict: FSes were OP and a mechanic that many serious Smashers would have disliked. At least they can *mostly* be turned off. (Damn Pity FSes, those guys at Sora, what are you thinking not having a flag switch for that?! >;()