rough ride in a 08 - normal?

today I drove my first 08 in our search for a pre owned Sienna. It was very rough - like we were riding on pebbly asphalt. Will try another at another dealer tomorrow - but curious if this is 'normal' - our old Previa is a very smooth drive. Would not buy such a rough ride, this dealer had not done the check over of the car, it came straight from the auction so maybe it was an alignment problem. It's an ex-rental, 46,000 miles.

Another question is whether the "Toyota certified" extended warranty is worth the extra price hike on dealership pre-owned over non-dealership dealers.

thanks for any replies concerning this.

PJ