I spent a lot of time as a hobbyist using Reason. I found it
super fun to play with, but I ran into two problems:
1. I almost never actually finished anything in it. That's a problem for me in general, but Reason exacerbates it. There are so many knobs to tweak, that I often ended up mired in the minutia of tweaking sounds. I found it hard to stay high level and focus on the music.
2. Compared to, say whaling on a real guitar or keyboard, I found Reason sounded very "dry" out of the box. To get something that didn't sound cheap or reedy, I had to do a lot of set-up: make a synth or two, wire them through a few effects and EQ, tweak everything, add some reverb, tweak some more. I felt like I wanted to decorate a cake, but Reason forced me to go out and thresh some wheat first. This level of control is really powerful if you're into sound design, but made it hard for me to make songs and music.
Of course, your mileage may vary. As far as fun toy to play with, though, Reason is a blast. I spent many a happy hour tweaking and playing with little loops.