I have the 17-55mm IS, 24-105mm L IS and 24-70mm L F2.8. Ive always had an IS standard zoom from my days in APC, If you are used to IS you will miss is. Its not that the 24-70 range doesn't need it, but the IS is a big shoulder with heavy glass and also makes the shooting experience nicer with the steady viewfinder.
If you are used to getting away with shooting between 1/30th - 1/80th you will effectively have to double it without IS and FF. I found moving from the 17-55mm to the 24-105mm a really great path. I thought moving to FF would be a bigger issue with the larger mirror/more slap and shallower DOF. But I love the 24-105mm, I had no issue with the move at all. It is equal in IS/IQ to the 17-55mm and served me very well for my first 2 years with FF. Its not the absolute sharpest but its a brilliant range and 90% of the time will be all you need until you get into low light conditions. I also have an exceptional copy which isn't far off my MKI 24-70mm which I think adds to my opinion.
Moving up from APC to FF the mirror is a lot larger and the slap is more pronounced so shooting without IS higher speeds are needed.
Im a wedding photographer and bought the 24-70mm F2.8 about a year ago because of its low light capability. When out testing the lens I found my keepers were well down, you'll find that you do need to ensure your SS is faster or you will end up with blurry shots, more lazy on my side because I'm used to relying on IS. After a couple of outings with it there was no issues at all, I also have the 70-200mm non IS so started using the same technique and it worked a charm. It doesn't take long to get used to but its also a lot heavier and a pain to lug around, so unless I'm on a job I leave it at home and take the more compact, bigger range 24-105mm.
The 24-70mm F2.8 is an exceptional lens tho and the results are incredible. Its just a different way of working and not relying on IS isn't a bad thing and improves your technique. I generally get 95% of keepers with my 24-70mm down to around 1/40th.
I would recommend the 24-105mm F4 over the 24-70mm F4 for 2 reasons - range and price. Its no argument the 24-70 F4 has better IQ but it is marginal, it has less distortion true but this can be sorted in post. A good 24-105mm can be had for £400-500. Also to say that you can't get great results with one check Sean Bagshaw out on flickr his images are astounding using a 24-105mm and 16-35mm MKIhttps://www.flickr.com/photos/seanbagshaw/Joshua Trees and The Galaxy
by Sean Bagshaw
, on FlickrHint of Winter
by Sean Bagshaw
, on Flickr
and one from me with the 24-105 and 5DMKIII Hallin Fell, Ullswater, Cumbria, starscape
, on Flickr
The Macro capabilities of that lens are useful but I'm not sure how useful as you need to be so close you would scare anything away.
Like you I will buy the 24-70mm F2.8 MKIII when the IS version comes out. ATM I feel the MKII lens is too expensive without IS if it had it I would buy it in a heartbeat. IQ may be exceptional but the 24-70mm MKI version is still stellar and not that far behind if you have a good one and leaves you with £1000 change. Thats a lot of money you could add another lens, I added the 16-35mm MKII with the money I saved, which I love shooting with.