I went on a "lime plaster for plasterers" course at cressing temple last year. it was done through the local county council, the guy running it was a mine of information, tips, Demos, examples etc - worth ten times what it cost!
I'm was expecting everyone else there to know a lot, but in fact everone i spoke to had never used it, and knew very little (problably why they went!)
Personally I prefer with lime now(either putty or NHL), With putty you get much longer to work it than with Gypsum, And the finishes can be better in some cases.
I think also that there is less physical work involved with gypsum. the rubbing-up time means and finish coats will take far longer than the same area using Thistle. Also knocking up takes quite a bit of effort.
Less and less people out there know much about it at all it seems. but the health benifits are clear - also so are the savings to yourself. If you can store it in your shed, you'll never waste any plaster again, chuck it back in the tub and knock it back up when you need it.