I used it regularly and I think it's excellent. A thin layer and then wipe down after 90 mins or so with grit 1500 gives an immaculate finish if you ate giving the bat some end of season tlc. Only takes around 2 hours to dry from my experience.Top quality product!
I don't know about turning it darker. Of course, oil will naturally change the colour of a blade, but with the wax, providing you only give the bat a light coat, there won't be too much change to the colour if the willow compared to raw linseed oil.