The walking speed is fine with me but I feel I'm running too fast. I'm aware of the player.setav speedmult console command which I'm using to set the speed to something like 75%, which is fine, but it lowers the walking speed as well. Any ideas on how may I change the running speed alone?

http://www.skyrimnexus.com/downloads/file.php?id=1931 slightly increases the movement speed while walking and reduces the running/sprinting speeds. I've found it to be VERY nice.

I'll definitely try this out, thanks!

I use Faster Speeds, by Wolfmark: http://www.skyrimnexus.com/downloads/file.php?id=1603

It allows the user to configure player running/walking speeds and horse running/walking speeds independently via an easy-to-use GUI.

You can also change speed without mods (to check what values you like) by console command
Speed is changed by percentage so if u want to run 20% faster it will be
player.setav speedmult 120%

EDIT >> sorry my bad i somehow not read first post -.-'

he mentioned that in the op.

One problem I noticed with the speed mods mentioned is that the speed adjustment only works for regular walk/run movement with no weapons/spells equipped. By default you are a bit slower when you move with a weapon drawn or with equipped spells. If you decrease your speed with one of these mods you may become faster if you have something equipped in your hands compared to empty hands. Stealth movement is also not affected. I assume there are different movement settings for these cases which aren't touched by the mods.

I think the mod paladin linked addresses that.

Ah, I think I looked at an earlier version of that mod and didn't look again. Seems like it was fixed then for that mod, thanks.

Yup, the mod paladin linked works just fine, the running speed feels just right and the walking speed is the same as the NPC's. It's perfect.