I use lower end Shimano SPD pedals on a number of bikes, 520 or 540 series, whichever was on sale at Nashbar at the time. I typically paid about $25 a pair. I assume there's a difference between the more expensive XTR series and lower levels, likely titanium spindles and weight, maybe better bearings, but nothing I would notice. I also have a pair of Shimano PD-M424, which are dual sided SPD with a dual sided rubber platform to allow street shoes to be worn. Heavy but really functional for my tourer/commuter

I've been mt. biking 30 years and am in the camp of using pedals that keep the foot attached to the pedal, to avoid the foot coming off the pedal in the rough stuff. I don't quite get the pinned pedal concept and how that keeps the shoe on the pedal when you are getting bounced around. People like them though.