Generally speaking I would say that the included Rapture presets, and the additional packs you can pick up, provide more than enough awesome keyboard sounds. And all you have to do is pick a preset.
I've been using the presets for years, tweaking here and there. And of course I've also enjoyed layering the preset sounds with other synth sounds to make all kinds of cool discoveries.
But recently I've been wading into the depths of actually using Rapture. By that I mean actually trying to design a target sound I have in my head from scratch.
Recognizing I really didn't understand the Rapture knobs and what the dials and buttons really do, I recently purchased the $5 SWA tutorial on Rapture from the Cakewalk store.
It's pretty dated and not up to current standards in terms of tutorials, but nevertheless I was pleasantly surprised at how helpful it is.
So I'm putting out a very belated positive note for this SWA Rapture tutorial in case there's anyone out there who has a bit of curiosity about Rapture and its features. It would be way better if Groove3 did the tutorial, but for when it was made and for the content it goes through it is very much worth the $5.