Hypersmurf
Moderatarrrrh...
Playing your way - locking in the flavour while free-forming the mechanics - will I think give a very different experience from 4e, perhaps something closer to OD&D or early AD&D.
I'm finding that I'm approaching running 4E with a completely different mindset to how I approached running 3E/3.5.
Let's say there we have a rogue with a +1 rapier, facing an orc.
The player alternatively says "I stab him with my rapier!" or "I kick him in the groin!"
In 3.5, I would have him make an attack roll with a +1 enhancement bonus, dealing 1d6+1 (+ Str) lethal damage for the rapier, or an attack roll with no enhancement bonus, dealing 1d3 (+ Str) non-lethal damage (and provoking an AoO) for the kick.
In 4E, I'll assume that the rapier is the Accessory for the power he's using (Sly Flourish, say), and I'll include the rapier's proficiency bonus and enhancement bonus in the attack roll, and he'll use d8 for [W]... for either the stab or the kick. The cinematic description is flavour; the mechanics of the power are the same either way.
Now, if the rogue doesn't have a rapier, and says "I kick him in the groin!", I won't let him use Sly Flourish, or Sneak Attack - he doesn't have a weapon to use as an Accessory for the power that meets the Light Blade requirement. With no weapon, the kick in the groin is an unarmed attack, so no proficiency bonus, no enhancement bonus, and [W] is a d4.
So the mechanics of "I kick him in the groin!" change, depending on whether or not he is holding a rapier.
I would never have run 3E that way. But if I ran a 3E game today... I'd now consider doing it like that.
As an in-game example - the Ranger PC was fighting a dinosaur, in a jungle clearing. He said "I throw my chakram up into the tree above the dinosaur, to cut loose two of the big spiky gourd-fruits, so they fall on his head."
If I'd been running this in 3.5 a year ago? I'd have accepted that there were big spiky fruits in the tree - that's cool. Then I would have assigned an AC to hit the stalks in order to drop the fruit. Assuming the attack roll hit, then I'd have had to figure out if they hit the dinosaur, and how much damage a falling spiky fruit deals. I probably would have given the dinosaur a Reflex save with an on-the-spot arbitrarily-assigned DC, and picked a damage figure that seemed reasonable.
In 4E? He rolled his Twin Strike using the chakram as the Accessory, and hit the dinosaur's AC with one attack roll and missed with the other. So one spiky fruit fell, and hit the dinosaur dealing chakram damage.
A year ago in 3.5, it wouldn't have occurred to me to assign the dinosaur's AC as the target DC for cutting a spiky fruit, or to assign the chakram's damage to the fruit. What about the range increments to the fruit? What about the size modifier? The fruit is Tiny, the dinosaur is Large! The dinosaur has a Dex modifier of +1, but the fruit is an immobile object with a Dex modifier of -5!
But if I ran the same scene in 3.5 today, I'd be tempted to do exactly that.
-Hyp.