Robert
This 'upgrade' was one of the first things I made with money raised from selling my prints. It isn't a cheap move, but one that I am pleased that I made. The ND grads are more neutral than my Cokin P, not that i had noticed manyproblems beforehand, it was just the way the pictures looked. Furthermore I do not know anyone who has switched who regrets the move.
Essentially I did tally chart from Joe Cornish's First Light book to give a priority ranking, since I was on a budget.
So I have ND hard grads in 0.3, 0.45, 0.6, 0.9. I then added ND Soft grad in 0.45 and 0.9 which are useful for water. A Kaisemann polariser with rotating ring, Joe uses Heliopan, I got B+W. Warm up in 81B, 81D and an 85C (which I have used 4 times in 3 yrs...), I then went off piste and got an 81B to clear soft grad. I use this inverted to warm up foreground without altering colour of sky. I reasoned that the softer grad would taper out in a subtle way into the haze present on the horizon.
Also a B+W set which are alright but flimsy. Apart from this B+W issue, I haven't bought any more in 2.5 yrs.
Make sure that if you do make the move, that you get Wide Angle adaptors for lenses of 120mm and less.
Sorry to spend your hard earned money like this, but your superb pictures do deserve it!