That's your call.
I'm looking at this lens or the 135L and 3/4 of my lenses are already at or have 50mm in the FL.
In my case, I got the 17-55 (to your 24-70) instead. Hope that helps.
the 24-70 isnt all that great unless you have one of the rare sharp copies. or you dont mind stopping it down... but then you might as well get the 24-105 f/4L which is a REALLY sharp nice lens and has more reach
Something I should probably add, and the reason i'm having difficulty deciding is the fact I don't currently own a lens that covers the focal lengths between wide and medium. I have the 15mm fisheye, and then the 50mm f/1.8, and nothing in between. Whichever lens I choose will be my 21st birthday present, so i'd like to choose wisely.
Then again, I know which I want, and which I need...hence the debate. I might check out a Sigma zoom to cover the FL so at least I have the lengths covered for jobs, and the 50mm for everything I can possibly shoot with it.
Edit: David - Awesome work, as usual. I'd like to hear your thoughts on shooting weddings purely with primes. Tough? Enjoyable? Does it ever weigh on your mind that you might miss a moment, or do you ever get frustrated not being able to zoom? And how does the whole 'change lenses mid-ceremony' thing go, if you do it at all? Love your photos dude. Very impressive!