I bit the bullet and bought G-wizard. I've

broken a couple of tools despite using it (only the expensive carbide ones, so that's OK then

), but on the whole I think I can credit it for keeping my tooling bill somewhere reasonable. I must admit, some of the figures it comes out with seem quite scary on the machine (like - "stand well back, she's gonna blow" scary), but it seems to work.
AIUI, if you buy G-wizard for a certain number of years, you can continue to use it once your paid sub has expired, within certain horsepower limits. e.g. because I bought a 3-year sub, I should be able to continue to use it once it expires, for up to a 6hp machine. I could be wrong on that...