I am using a 50mm 1.4... that is one hell of a lens with great results at 1.8, and amazing bokeh...
The problem is that having three prime lens, is good in theory. But you also have to carry them, change them continuously which becomes a hassle eventually. 24-70 is good for portraits, weddings/functions and landscape... and gives you a pretty decent bokeh if you can get the depth of field...