ARM Cortex M has the disadvantage of having too many options which really muddy's the field for hobbyist's with too much information overload.
I spent $150 on Rowley Crossworks non-commercial and a J-Link EDU version, just because it's easy and I don't have to mess with anything. It's about as easy as MPLAB-X, but then again, some of you guys have problems with that.
Whether it's worth it as a hobbyist just depends on the type of projects you do. If you don't need it, you don't need it. Quite frankly some of the 8 bits have gotten rather fast with updated peripherals that are pretty nice.