I’ve got a Pivot Mach 4 DW link bike and have found it to be the best for me so far. I’ve owned most designs over the years (Klein Mantra URT, Haro Extreme single pivot (think Santa Cruz), Trek Fuel linkage activated faux bar, Stumpy four bar and Intense Spider VPP) and am enjoying the Pivot more than any of them so far. Theres no pedal bob, no noticeable pedal feedback and its really plush. You can run crazy sag – had 35% sag today as an experiment and there was no wallowy sogginess pedalling just buttery smoothness. It has an RP23 propedal shock but i’ve never felt the need for the propedal (even honking roads or bridleways) – i believe Pivot specced the RP23 shock because they believe it is the best performing air shock out at the moment regardless of whether you need the propedal function. My previous favourite was the VPP Intense which i thought was pretty special but the Pivot is a yard ahead again.
Haven’t found any downsides yet.