Driving a tracked vehicle at 35 mph does NOT feel slow. I had hundreds of miles running M-114s (post-rebuild test drives - we took them off the end of our line and ran them around the plant after regular working hours so as to not have to worry about runniong over people) at USAMP-Roedelheim 1966-67. It is a fun little track on hard-stand. Noded easy and got stuck crossing ditches, though, plus short on power and had a less than perfect "Rubber-band" track instead of shoe-type live track like the M-113.
A diesel version and new track, plus a revised front end configuration would have made it better, maybe even worth having. They were alo prone to hull cracking where the final drive exited the hull. Part of the rebuild we were performing was to remediate any crack that were not too severe and add a somewhat complex (in shape - it was just a slab of aluminum cut to fit around the final drive axle penetration for the drive sprocket) reinforcing plate by MIG welding to all vehicles.