There are a couple of differences between Rage and RP though; RP is only generated when you use abilities that expend Runes. You don't regenerate it through normal melee attacks, from incoming damage, or from abilities that use RP to activate like Howling Blast/Dancing Rune Blade etc.
The display of Runes and RP has changed about four times already, Blizzard seem to be having a really hard time deciding on how to do it.
At one time it was a glowing aura on a picture of a sword next to your portrait, and the glow got longer if you had more RP (cant find a shot of that anymore...).
It's also been a little crescent-shaped blue meter that grows upwards next to your portrait:
http://wotlkwiki.info/up2/pages/dk/quests/2ufq98z.jpg And it's currently a very boring horizontal bar like Rage or Energy as you can see in Billie's shot.