greg, kinda off topic...but I'm a Mobil 1 user, too. Also, AmSOil ATF. Lately, I've been routinely getting 400 miles per tankful, in town, on my Ody which rarely sees any highway miles as my commuter / family-of-six taxi vehicle.
The engine is a little quieter, most noticeably on startup, with M1 in the crankcase. The AmSOil ATF difference? Shifts feel like when the car was newer, and it sure seems to coast a little longer when I ease off the gas pedal. Just changing to these fluids, without changing anything else (tires, tire pressure, driving habits, weather) achieved these differences and going from low 300's to 400 miles routinely on a tank of gas.
So, back to topic. I think the O'Reilly synthetic is "safe" (if it has the proper API classification). And yes, with M1 (or other high quality synthetics) you're paying for "a name"...but usually that "name" means they have a team of petrochemists continually working the angles to put their product's performance delivery as high up in the marketplace as possible.
But, the OP's question of "how good is it? (O'Reilly synthetic oil)" Probably "good enough", but that's all I can say. I can't even say if it's better (or worse) than the best dinosaur or dino-syn mix oils out there.
OF