I saw some in my LFS, I don't care for them. I think they're a little tacky, sort of like a more humane version of dyed fish. IMHO fish that occur naturally or almost so are the nicest looking.
my daughter talked me into buying a couple. they were far more fragile than normal danios, they didn't stay still long enough to tell the difference and they all died very early.
I would buy GM fish if they could garentee there are no side effects.
Changing a gine could mean changing lots of things. but i would if there's more info and research done on the DNA of fish
I don't think there would be any major 'side effects' as these fish are being bred and sold to the public, if there were any major side effects then i doubt they would be bought by fish shops and the public and wouldnt have been bred on a large scale in the first place, although they might have slightly different characteristics such as being slightly less hardy.
Also, they've been in existance 10 years. If there was any major effects from the change, you'd think they'd know by now. They've literally gone through 1,000's of generations if not 10's of 1,000's so they've had time to see any problems and none have been reported.