I have to admit that I have always found my 24-70mm (and 28-70mm f/2.8L before it) to be among my least favorite lenses from a creative standpoint.
That said, i do reach for them any time i just want to be able to shoot fast and get good results.
If I need more light, then I go for faster primes, but the 24-70mm and frankly 70-200mm zooms are going to be versatile and let me work much faster with fewer restrictions than a prime.
I lived without a 70-200mm for several years recently, but was compelled to pick up the Tamron with VC for a shoot where it proved invaluable.