I spend hours upon hours just jumping from places.

It never occured to me to think about WHY it was so much fun until I read your article.

I guess it comes down to the sense of freedom it gives you.

Raw speed is essential to give you a sense of freedom.
Controls that result in a slow response on screen (a slow moving char) give me the impression of restriction and can even evoke a "claustrophobic" feeling, so I'd always favor faster movements.

But raw speed is only one of the benefits.

The other one being your ability to "move differently".
Getting down a hill by running down the preset path with your new gained raw speed is fun, but it's even more fun when you're able to just jump right over the edge, down to the ground and land with a cool looking shoulder roll.

Again, this could be summed up as speed, you're getting faster than usual from A to B.
But the way this is done gives you new options (leaving preset paths) thus enhancing your sense of freedom.

Anothe example being Super Metroid.
It's such a great feeling when you acquire the powerup that lets you gain height by constantly performing somersaults in mid-air.
Even though you had the High-Jump Boots by then, they suddenly felt (a little) outdated because the somersaults gave you even more freedom.
You were no longer restricted to plattforms you could land upon/jump from, now you could just move through the air to... wherever.

I think in the case of Gothic I, which didn't rely as heavy on jump 'n' run elements as SuperMetroid, the standard movements would have been sufficient if I never knew that there were these acrobatics (or if they never had been implemented) but as soon as I got them I had this moment of realization: "So now THIS is freedom." I never knew how much I was missing.

These full-tilt chase sequences really get the adrenaline pumping. And its a nice reversal of the usual gameplay situation; usually the player fights things one by one and overcomes them all, but this thing was so much bigger and nastier than everything else in the game that there was nothing you could do but run away from it, fast.

If movement abilities like this are included in a game, it could be worthhwile to design movement-affecting environments. Similar to how particular attacks might excel in one combat situation and meet their own personal "cryptonite" in another situation, movement abilities might have both optimal environments and difficult environments. An area with strong winds and lightning might make flying difficult, while the trap-laden terrain of another might make flying particularly advantageous. A maze-like area with short paths and sharp turns might somewhat negate a player's speed ability, but speed might make it infinitely easier for that player to catch the creatures of another area which are infamous for running away before death and being speedy devils. Those creatures might even be in an open area at the end of the maze, thereby using the player's frustration to build tension before a big release and revelry in his speed ability.

I'm a big fan of dynamics and replayability, so anything that significantly differentiates one play experience from another is of great interest to me.

Yeah, movement abilities mean that the developer has yet another thing to balance for. People complained a lot in WoW about the Druid's travel form ability, because you can cast it instantly and you can't be disrupted out of it. So, many times a Druid could outrun low- or mid-level enemies; a quick Druid could even outrun higher level enemies that had to take time to summon mounts.

So, yeah, it's gotta be considered carefully.

And I've jumped off the sides of cliffs to cheat death from mobs and other players. That one is my favorite - they think they have me cornered, this little frail flying thing and as they advance, I turn and leap to safety.

HUGE PVP ramifications. Suddenly one race has an advantage others don't...

What Saylah mentions in her comment, and what you're driving at in your post, is the 'feel' of doing something more than running. I think that's completely what the movement powers are about. I never *felt* more like a hero than when I was using my movement power. I respecced to super-jump later in my career, but when my primary in CoH first got a movement power it was Flight. Several buddies of mine also chose flight, and the four or five of us soaring across a zone together was completely awesome.

The ability to do something different from our daily lives is kinda the whole MMOG thing, after all, right? That's one of the parts of the appeal of WoW mounts. I'd give my eye teeth for a ridable velociraptor! It's also something I think Vanguard *mostly* has a bead on. You can own a ship, and you can fly on a blimp, and you can ride on a pegasus ... but their horse looks like it has terets.

And yes, planning is important -- it's certainly the reason there will be flying mounts *only* in the expansion zones in WoW:BC.