On-topic though.....
I really do prefer the standard D&D "per day" mechanics for general balancing, with "per encounter," "per session," or "per in-game hour" stuff being secondary and used just for certain kinds of mechanics. I like a good mix of stuff, and would like to see every character do something effective all the time, but would prefer many of them having a focus on really cool stuff they can do only once in a while, being only mildly effective when they use up that limited resource (it makes for good tension and helps balance the use of really-cool stuff like Wishes, Fireballs, Teleports, etc.).
Especially since, for instance, hit points are the one great limiting factor for Player Characters, that which defines how long they can fight. Infinite full-healing breaks D&D, especially if it's in a campaign where the other PCs also have infinite power reserves (Warlocks, Dragon Shamans, martial adept classes, etc.). Example: A 5th-level Cleric with the reserve feat from Complete Champion that gives infinite healing capacity could proceed to multiclass into Crusader afterward, then the group essentially has infinite fighting capacity. They are unstoppable juggernaughts that heal up quickly between battles and never stop marching forward. A party of Cleric 5/Crusader X, Warlock X/Swordsage 1, Dragon Shaman X/Swordsage 1, and Warblade X, could be pretty scary.
Reserve feats can be troublesome, moreso than a Dragon Shaman's auras, like their infinite fast healing aura (cuz it's got a hard limit on how far it can heal someone at any given time, and it's a relatively slow rate of healing in-combat). I don't have much of a problem with Dragon Shamans, because of their limits and because I've played one to see how they work in actual play. Their fast healing will lessen a Cleric's load in the healing department but going into battle half-healthy is half-likely to get you killed if that happens to be the 'grand melee of the day', so to speak.
So it's not a bad ability. But reserve feats or similar seem like they'd mess up D&D's functioning to some extent. If your HP are fully replenished for every fight, when do your heroes ever get tired and stop blundering through the dungeon or whatnot? When do they start to behave realistically in getting tired? I demand a certain minimum, vague, modicum of realism in my D&D. The Unstoppable Juggernaught (X-Men villain) is not a D&D character.
A lot of abstraction is fine, but I'm not going to believe that Tim the Wizard can trudge through a dungeon all day, cranking his crossbow endlessly to fire bolts, or calling on some infinite reserve of magical energy to blast everything into oblivion time and again. There's gotta be some limit. Otherwise why isn't everything else going at them full-bore? And if there's some infinite reserve of stamina or magical energy, why doesn't every archmage handily destroy all opposition by drawing on an obscene amount of that infinite reserve all at once? It just gets silly at that point.
Anyway, I just prefer to have mages and such limited to harnessing so much power in any given day, week, or whatever, before they need to stop straining their minds to bend reality to their will, so as not to make their heads 'splode. And to be capable of awe-inspiring magic when they do have enough energy at their disposal. And not just 'awe-inspiring to the sight of Joe Commoner who rarely sees magic in the first place', but 'awe-inspiring to the warriors and knaves who ply more mundane skills primarily'.
I like the Book of Nine Swords, and I like anime-type stuff (I'm one of those wierdos who actually likes FF7: Advent Children despite some of its flaws as a movie), but even in anime and video games the characters have limits. Cloud doesn't unleash one Blade Beam limit break after another when he fights Kadaj's gang, for instance; he builds up some steam, fighting normally, then has enough energy for a special attack after a few minutes of intense combat. And he didn't do everything in one day, either. Each time, he fought a little while, got beaten up some (rather badly in some cases), then retreated or got pulled out of the fight by a comrade, going to rest and recoup for the next day's chasing and battles.
It'd make a good case for a Warblade, probably. Some maneuvers available for one fight, running outta steam, losing most of their hit points, then retreating. Next fight of the day they have all their maneuvers back, but they're still low on hit points, so they can't fight very long and have to make the battle short. Then find a healer or something, rest up for a day before doing it all again.
But I'd still like to see the mages flinging spells with a hard limit on their number of 'cool tricks and explosions' per day, even if they may have some infinite-use minor abilities too. I'd have no problem with, for example, a Wizard who possessed some 1st and 2nd level maneuvers, maybe even a few 3rd level maneuvers at upper class levels, so he could do something effective and cool in every fight (assuming he has a maneuver recovery mechanic that's less sucky than the swordsage's).
He just shouldn't be able to nuke everything to holy h3LL in every fight, yet he should be able to do so every once in a while, cuz he's devoted his time and efforts to mastering the arcane arts, sacrificing physical development and personal combat skills toward that goal of unmatched eldritch power.
Per-scene, per-session, or similarly abstract time mechanics can be really odd and unbalanced (or just plain nonsensical from an in-character standpoint) for a game like D&D. They'd be fine for some kind of action points or hero points, assuming it's a limited set (like, you can do 3 kinda-cool stunts per session, or you can do 1 crazy stunt per scene/adventure segment/episode/chapter), but not for most general mechanics, like special attacks or special powers. At least not so well when it's on the scale of D&D's wizard spells, dragon breath, or whatnot.