The main reason is, that with first person camera, player will feel that he is really performing some stunts (sure if u make them realistic enough).
That will bring one of the main thing in every game, the atmosphere... That u r a Tracer...
With 3rd person, it will be something like circus I think, player will just make some stunts, will think:
"dude, it so awesome, I can make flips and vaults while shooting every one, so cool..."
Sure, sounds great, but player will miss here feeling that he performing stunts himself...
And BTW, aiming will be easier with first person camera... Well I guess there are no much to say, just compare:
FPS (Mirrors Edge)
3rd person (Free Running on PSP)
I know, that these are two incomparable games (even different platforms), but good example of FPS and TPS.
Just try to image, how your player will be able to shoot in TPS while for example jumping from one pole on to other
And u'll make right decision I can't really see comfortable aiming in TPS..

You brought exactly the point that keeps bothering me... I'd love to try a first person perspective, yet there are two things that still keep me from going "alright, let's do this"...

a) I'd really like to make a third person game. I know it sounds silly but I'd just like to try on one. And, well, the idea of doing a third person mp shooter came to my mind BEFORE I had the idea of spicing it up with parkour/freerunning...

b) Some things will be incredibly harder in first person, from the view of a developer. For example, if I'd do a first person view, it'd be a "real" first person view - no floating hands with weapon and another model for the rest of the body or something like that, just one model. And that would make things like aiming down sights more difficult to realize.
Also, the generel detail, graphically speaking, would have to be higher.

Well, you see, I'm confused.

Make a TPS, but why should it be with parkour?
There is no way to make good parkour shooter with 3rd person camera!
About player movement and camera in FPS, I'm sure that making realistic camera movement isn't that really hard (u know that u can use animations for that).
Try to make movement like in Mirror's Edge (of Dark Messiah), I think u'll learn a lot of new stuff and I'm pretty sure u'll succeed!
Make it FPS, and u will not miss it

I guess I'll just have to try both... most of the movement code will be similiar either way, guess I'll do the basics then try several perspectives.
I'm still more fond of a tps view, even though I actually prefer first person for shooter games. However, we'll see.

Maybe this is over the top, but if you're focusing on movement, THIS is what i'd love to see:
http://www.youtube.com/watch?v=29ZEvxwq_F8&feature=related

One day I'll program a game where movement will work like that...

Edit: check out the rotation on the pelican. That rocks!

Ohh man, I wish to have this with GS So realistic...

It CAN be done with GS. Just needs some pretty advanced coding.

Sure, but I'm not able to make it myself, I was hoping for it to be build in
jcl said that all we need is to make trace from each leg, and change bones angles and blahblahblah...
But that is just how to make 1 feature (adapting to slopes,stairs) from few huge other feauture that Locomotion has...

You cannot built sth like this into an engine...

You just would have many problems..

@3run: There isnt' anything in this vid that cant be done with GS. You just need to know how to do
a) proper procedural animation blending
b) Inverse Kinematics.

The Latter is a bit difficult, but a) is rather simple compared to b).