I'm planning on getting the Mark III soon but I'm torn about which first lens to get.

I was thinking about the EF 24-70mm f/2.8L II USM. to cover most shooting scenarios.

Is anyone using this lens or would you recommend another lens?

Thanks in advance and happy New Year!

At the very least this should be your first lens.  Your second lens should be a 70-200 f/2.8L II

You won't need anything else for a very long time.

I have owned and sold two copies of the 24-105L.  That lens sucks.  It sucks light out of things.  I've been walking through Downtown Denver at 10am in the Spring and have had to up iso to 400 because the lens just sucks light.  Get fast glass - you won't regret it.  I have not had ANY problem with chromatic aberration with the 24-70.

If you feel like spending more money, then a 50mm f/1.4 and an 85 f/1.8 should go into your bag as well for those extremely low light conditions