Saw a video yesterday showcasing all the Disciplines at lvl 5, pretty interesting. I never bothered with Fortitude when playing Gangrel but that thing at lvl 5 is OP! In the video he was hit by knives and shotguns over and over and the healthbar barely budged! Combine that with Protean War Form and man - you got a fighter! Also Pestilence for crowd control. Seriously, I didn't do my Gangrel justice.
Also I think I've misjudged Celerity. I tried it at lvl 2 and 3 when playing Toreador and I was unimpressed. Yeah the world slowed down but my character did too and it felt like moving through molasses. But at lvl 5 it seemed to be better because the character moved around pretty well while the enemies were almost frozen!

I was even impressed by lvl 5 Auspex because you could see all the enemies in an area through the walls at a great distance which was very cool.