I have a single AK48 mother. Started with 10 seeds, only one female survived. Can't blame Nirvana-- in my case it was user error. I forgot I was germinating them and went 3 days w/o checking the paper towel. Mold had gotten them.
The one female that survived has become my staple mother. Grows fast, takes extremely well to cloning and supercropping, great yield, smells like fruitloops, amazing gland density and nice dense buds, and a smoke that's more sativa than indica.
I usually top 3-4 times and prune the bottom 3rd. End up with 30" tall plants with 8 -10 tops in a nice bushy canopy. Produce a little more than a zip per plant dried. And YES, it flowers very fast-- right about 48 days.
I can't say if there are less desirable phenos because of my bad. Maybe I got lucky. But Nirvana's AK48 gets an A+ from me.