Please - would you who are experts here maybe advice me about if to upgrade from my newly purchased Canon EF 300 f/2.8L IS USM to version II?

[HDNitehawk]

Yes maybe I should buy the 1D IV - and is this a fullframe only or do the 1D IV a crop-sensor camera=?

It is not 1.6 or full frame. The crop on the 1D IV is 1.3.

For example I find myself avoiding Canon EF 14mm f/2.8L II and I rather use in real life in the field and outdoors instead the better Canon TS-E 17mm f/4L, because it delivers better IQ compared with the 14mm even version II when I closely work with them in my computer! I still lack a good 24mm and I have even avoided to purchase the EF16-35mm Version II ...I think I should go with L-primes rather...but I found the light weight EF 70-200mm f/4L IS USM with one flourite lens element to BETTER than my new EF 70-200 f/2.8L IS USM II - and this lens is now for a check up at the Canon Service center here in Stockholm because it could not deliver as sharp images compared to the excellent EF 70-200 f/L IS USM ...but again that may only be the case with this one I got now for only about two months ago...but I think the version II of EF 70-200mm 2.8L IS USM should be at least AS SHARP as the older 4L IS USM=?

I had a 14mm for a few days and it was very sharp. I think if this is a real concern for you, stay away from the zooms. The primes are much sharper. The 16-35mm II is a fine lens, but you will get better quality out of the 24mm F1.4 II L and the 35mm F1.4L.

I am still struggling with not getting acceptable images even having almost only Canon L-lenses.

I don't know what to tell you here. The L series lenses are the top of the line. If you are looking just at the best IQ, primes are better than zooms. I own the 70-200mm Version II, it is the top of the food chain when it comes to zooms.