I have reference dots on the fingerboard (as opposed to the side of the neck) of my NXT5, and find them helpful for keeping intonation, obviously. However, their presence also makes me look at my fretting hand far more often than I do on my other upright, and that's something I'd prefer to avoid, especially as I tend to read as opposed to memorise (I know, I know!). So it's a bit of a mixed blessing. Musical ear and muscle memory are best.