Unless you think you will be able to pick everything up first time (some can, not me alas), then I think it is worth it. I certainly sensed I was not getting the hang of NDB holds in one lesson (as I hoped) so I bought Rant to practice. It works for me, but may not for everybody.
Did it save me air time? Difficult to guage. My guess is that it certainly helped and subsequent lessons went well. Still use it occasionally to brush up. so it has longevity.
Just in case you were thinking it: Personally, I didn't find Flight Sim any help (that has been a waste of cash for me) as I find I spend most of my time setting things up, reseting and reloading after it has crashed with pretty terrible performance to boot. Very fiddley and annoying.