Experiences and opinions welcome....

I like their barrels, they were my choice on a recent build but I could never find them in stock.

As far as piston vs DI, I prefer a properly gassed DI. I keep a cleaner gun than is probably fashionable, I treat with froglube or fireclean and carbon build up is not a problem.

Unless you really want a 5.45 AR (corrosive), there is no reason to get a piston, and plenty of reasons not to, unless (possibly) you want to run a suppressed SBR/full auto with a decent round count on a regular basis. Otherwise, DI is: lighter, more accurate, standardized/cheaper parts, no carrier tilt, and lighter recoiling. Furthermore, if I had the dough to suppress and SBR stuff, I'd probably look into a SCAR for that role.

That being said; if I got a reeeeally good deal on one, I'd buy it, but I would say you can get a better gun for less money in DI. If you want it just 'cause you want it, then go for it.

The answers above cover it well IMHO.

The older Adams Arms gas blocks are pretty tall, there is a very short list of rails that will clear it and the piston rod.

The newer updates are shorter and more options, but check their website for the latest list.

I handled one of their factory uppers, it was bulky forearm tube compared to the DIs next to it. Didn't take the look any further.