Unlimited healing ... has a bit less plausibility for me, I like healing surges. The idea of inspiration and luck and energy being "deep resources" in the subject is cool to me.
I really don't like them. They make no sense. How do you, for instance, "spend" a healing surge on something, like the healing sash? Theres no parallel for this in any fantasy movie I've ever seen, or in reality. You can't have "Joe from Wisconsin thrown into a fantasy world, picks up a sword and starts fighting" because DnD characters just don't work the way you and I and even movie and fantasy people and characters do.
Saying it's "luck" doesn't work either. Characters know exactly how much they have. Do you know how much luck you have? Does anyone? Nope. And again, how do you "spend" your luck activating a magic item or to heal someone else completely? I certainly can't spend my luck that way, maybe it's not a surprise I can't picture it and no film-maker I know of has tried.
If you're "bloodied" and rest for 5 minutes but then fall off a cliff, you die, but had you "spent" a couple healing surges, you have enough HPs to live. Weird. So "luck" didn't save you from dying from the cliff, but had you spent the surges and had less "luck" left, you'd have lived. Weird.
What does someone with no healing surges left look like compared to someone with full? I dunno. 4E didn't even try to describe it, like they didn't try to describe what it looks like to use healing surge. Because, well, they can't really.
What it comes down to for me is that all characters in 4E possess magic. It's the only good fit for how surges work. So even your bog standard fighter can magically heal himself or power magic items. You don't have to be a sword mage, everyone is doing it!
Though I also like potion interaction limitations, ie if you take potions while you are still under the influence of a previous one (how long does a healing potions influence last?) then you get unpredictable and or dangerous results.
Um? If you have 10 surges, you can chug 10 healing potions and they work, 10 more and they do nothing. Alternatly you can spend 10 surges on powers and then the very first potion you try won't even work... even if you wait 3 days without taking an extended rest. So "influence of a potion" makes no sense what so ever. It's a really ugly shortcut they took to try to force characters to rest frequently.