I have one. Mine has been an excellent rifle. Being a piston AR naturally it is going to be more than the Bushmaster. However for a piston AR it is a very good deal. You can't get most piston uppers for the price of the complete Ruger.
Some have experienced carrier tilt and had some buffer tube wear. I haven't seen any on mine. I have close to 1000 rounds so far through mine. Carrier tilt does not affect reliability and has been a phenomena experienced by all piston AR manufactures at some point. There are a couple different ways to prevent or minimize it. Ruger stands behind the SR-556 and I know one guy that had some wear over the course of 1500 rounds. He called Ruger about it and they wanted to look at his rifle. They sent a brand new rifle to him.
Here are a couple pics of the Ruger along side a AR build on a Anvil Arms lower and upper with a Lothar Walther barrel.
Please excuse the "fishbowl" effect in the 2nd photo from my cheap camera. lol!
Some don't care for the pinned railed handguard.
Accuracy is unusually good for a piston rifle. Mine is comparable to a DI Rem, Bushy or RR. (Not with that junk Wolf ammo on the table. lol!)
As much as I like mine, it probably wouldn't be my pick for a calling rifle. I don't care for a railed handguard on a calling AR. Plus the piston system adds a little weight. One of the others you mentioned would probably be a better pick. For a really light handy calling rifle, an M4 with a float tube is hard to beat and inexpensive. Very light, accurate and handy too.
Have you considered D-Tech? I don't have one of his rifles but I've yet to speak to an unsatisfied customer out of many. He incorporates all the important features needed in a hunting AR and will build it how you want it instead of being stuck with features needing to be changed. If I wasn't going to build one myself, I'd go with D-Tech over the factory offerings. Nothing against the factory rifles of course. They are great too.
Good hunting