There are pros and cons for almost any paint you can think of. When it comes to JDBB you'll usually find most professional painters will tell you not to use it. On many levels they're right. There are a lot of alternatives that will give you the same look but none of them are as inexpensive as JDBB.
I shot the frame of my deuce using Hot Rod Flatz satin black and although it turned out OK I wasn't happy with how it sprayed. When it came to the firewall I decided to experiment with JDBB. I figured that if I don't like it sanding it all off a firewall will be easier than a larger surface so it was a good canditate for a JDBB experiment.
All that said, I liked the way JDBB sprayed and it certainly was cheap enough. As far as color and sheen it matched the Hot Rod Flatz exactly. However, only time will tell if this experiment will work or if it was a mistake. At least then I'll be able to speak with experience when it comes to using JDBB.
Some things to think about....when considering using JDBB just understand that it is an enamel and not a urethane so even if you use the hardener it won't be as durable, but it will be less expensive. It will also require more work if you ever want to change it. Repainting something that is coated with JDBB WILL require you to sand the JDBB off first. There may be a sealer out there that will work over JDBB but I'm not aware of one that has been proven to be fool proof, so just be warned.
So basically its a trade-off. Cost vs. durability and ease of re-coating. I'm not recommending JDBB by any stretch of the imagination, just do your research so you can make an informed decision.