[Jack]

I do/have in some cases.
I can tell you this: in 99% of factory chambers, the neck of the chamber is too large to benefit from neck turning. It's a waste of time, and wears out cases more rapidly.
In a custom cut chamber, or a very rare (very rare) factory chamber that has a rather tight neck, you can get some benefit from neck turning, assuming a rather accurate rifle to start with.
I wouldn't bother unless the rifle shoots well under an inch already, and you have need for that kind of accuracy or better.
Haven't used the RCBS tool. I have used a Forster- the old one that worked on the case trimmer, and I currently use a Sinclair NT-3000 neck turning tool, which is much more precise than the Forster.
Generally you want to turn case necks as little as possible- just trim down the high side a bit.
Neck turning is one of those things you *ahem* turn to when you're trying to get an accurate rifle to shoot sub 1/2 inch groups.