It's a good gun... but as others have said, it's ridiculously overpriced just because it has the HK stamp on it.
If you want to pay a 50%+ premium just for those letters... then by all means, go for it.
I'm not a big fan of piston AR's either. I started with piston AR's because I bought into the hype of how much 'more reliable' they are.... Yes, mine were reliable... but so have been my Daniel Defense and ASA AR's. It was the non-standardization of parts on the piston guns that turned me away and the simplicity of DI that turned me on. Also, the lower felt recoil and accuracy improvements.
I don't think is going to tell you that the HK is a junk gun... it's not. It's just that it doesn't give you any benefits over a top shelf Daniel Defense, Bravo Company, etc... or even LWRC if you really want a piston gun - although the price difference there isn't quite as huge. I think LWRC is a bit over priced as well... still good guns though.
Glock 19 G4 BFG | Glock 17 G4 FDE | S&W M&P 22 | S&W M&P 45 | S&W M&P Shield 9 | Ruger GP100 4" | Sig P226 MK25 | Sig P229 Extreme | Sig P320F | Sig P320C | HK USP 9 | HK USP 45 (Tan) | Walther PPQ 9
Daniel Defense DDM4 V4 | Arsenal SGL 21 | ASA SBR | Savage Mark II FV-SR
Mossberg 590A1 20" SP | Mossberg 500 Cruiser