I'm a pro musician and I found the Midjay extremely useful. I sorta wish I still had one in fact. It would be a killer combined with the SD5.
There are so many great styles around I didn't see a need to create my own, and I haven't for quite a few years now, even though most arrangers have that facility.
If you are writing and creating original music I could see where you would need to create a lot of styles though.
DonM