The bag is mostly used for carrying my JD-Xi and storing it at home.
The build quality is good, it has two pockets on the front, big one and small one. The big one I use mostly for instrument cables and papers (it can easily carry A4 books). The small one I use mostly for carrying the power supply. It also has a two straps on the inside to hold the goose-neck mic.
The bag does what is supposed to do, it protects the synth. The only reason I have not given it 5 start is because it is not water resistant. Because of this I have not yet tried it in the rain since I tend to avoid that situation.
It is moderately thick as well, so it will protect the synth from all the bumps and hits that may occur.
Overall, I would recommend it since it is essential if you plan to carry your JD-Xi as opposed to keeping it in the studio, but for the price Roland could have included a few more features, in my opinion.
PROS: Good quality, good protection
CONS: Not water resistant