I got RDK 2.0 and I'm happy to report that it is all one needs... there are ALOT of samples on this thing,, I thought playing them on the midi-controller would be the hard part, its not... scrolling through a million "awesome" snares trying to find the best one was torture. I would go with reason, cause you have all the mastering tools right there with it.. The samples are the best I'v heard!
If I had to include a weak spot it would be cymbals, but thats only on the 16bit version, on the 24bit version everything rocks!! Unfortunatly you have to practise with the 16bit version and when you have your final song then load the 24bit version into the pattern to replace the 16bit... Unless you have a "massive" computer, there is no way to play with the 24bit samples in real time.