Coming from a 60D (8 years with crops) to a 5DMKIII last year i too felt thrown by the change in focal lengths.
I spent almost 5 years with a 17-55IS f/2.8 as my main walkabout lens. For me the 24-70 range is as close as i can get to what im used to.
I had a 15-85IS for a year, just before getting my 5DMKIII. 15mm on a crop was the widest ive ever gone, and hardly used it, so 24mm on FF is fine for me but i do miss having a longer reach. most of my shooting is done at the longer end of my 24-70, i do hit 70mm a large % of the time.
I'd say the 24-105L would be the ideal lens but ive never really liked that lens. Its just boring to me. I also like to do a lot of hand held night photography, and although i have primes would prefer to use a zoom, so i wanted something at least f/2.8.
Not much choice really. I had two copies of the Tamron 24-70 f/2.8 VC but both had issues. Shame as that lens seemed perfect on paper. I can shoot fairly slow with the 24-70 but nothing like 1/4 sec i could with a stabilised lens.