Dana, I own two 12-string basses. I have a MkII Galveston and a Carlo Robelli model. They were produced in the same factory in South Korea as the Dean Rhapsody specimen, and are essentially identical to one another and very similar to the Dean other than body shape. Are they heavy? Yes. Also, there is considerable neck dive. Are they difficult to play? Yes, at first. You have to get used to it. This is not an instrument you can "shred" on in the traditional sense. Are they useful for rock and metal? Most definitely! I already do that! If you can keep a clean bottom and keep your overdrive/distortion in the high frequencies only, it sounds absolutely massive. The best example of this is on the early King's X records. Doug Pinnick played a Hamer Chaparral 12-string bass quite a bit on 'Gretchen Goes To Nebraska', 'Faith Hope Love', and the S/T album. The King of Klang! I hope that this helps!
What band are you in? I live in Orlando proper, and I get out to a lot of area shows.
Cheers,
Bill