I think this is one of those matter-of-opinion things. Everyone swears by his or her pedal system.

Like saddles, it's a personal thing.

What did you feel was *wrong* with your SPDs? What advantages where you hoping to gain from the ATACs?

People who tend to rave about ATACs usuall ride/race in muddy areas. They tout their mud-shedding abilities. The downside can be that it takes awhile to adjust to the "point of release". It's a bit different from the SPD.

I dunno...but after years riding and many muddy races, I've pretty much accepted the fact that all mtb pedals clog in the mud.