I'm trying out split grade but the problem I'm having initially is the correct amount of grade 0. The two grades look OK as separate test prints but when combined seem a bit muddy. What I'm doing now is getting the grade magenta time and exposing a whole sheet with that time. I then expose a max yellow test strip on top of this to get an idea of the ratio. It's very early days for me in the darkroom and I'm sure it will get easier with experience.
One benefit I'm seeing to split grade printing is it's helping me to identify problems with my initial film exposure as I can see deficiencies within certain exposure values. The other main benefit, as Dave Miller pointed out, is being able to dodge and burn highlight and shadow separately.
I've posted a work print that I tried with split grade printing. It printed OK on grade 3 1/2 but the problem was if I tried to burn in the highkey areas is also burnt in the black accentuating the high key look.