I have one. I have been using it almost exclusively as a 300BLK. It shoots well and runs fine with subs suppressed and unsuppressed although I don't really see a need to run subs without a can.
Anyway, I tend to agree with the posts here about the need for a QD barrel. As the upper sits, the forend is a unitized piece of the upper so I'm only saving something like 6" by pulling the barrel. I also don't really see the need to go switching barrels back and forth back and forth just for something to do on the range. With that said, Ruger didn't jack the price up on the TD version so people who want the QD barrel can have that feature without paying an inflated price for it. Plus the new gun has a better (lighter) barrel profile than the existing SR-556 line and the rifle ships with some better furniture.
At the end of the day, the barrel feature is there for those who want to utilize it. Others, like me, can have a piston-driven 300BLK that can be easily pulled apart for an occasional detailed cleaning.