i bought a trek 7300. for the first month, it felt like i was using different parts of my quads than when i rode my d-back comfort bike. generally, i could avg 15mph on my d-back w/o much of a problem.
however, on the 7300, i struggled to avg 13mph even tho the gearing is significantly more aggressive. also, it seemed like the slightest change in wind or incline had an exaggerated effect on my ability to maintain cadence and speed.
at my 1-month tuneup, i noticed that when the tech's went on test rides, they would adjust the saddle much higher than i had it. i though this was odd considering they both were significantly shorter than i am.
i lowered the saddle about 1/4" from where the tech's had it and it still seems high to me. otoh, i went on my longest and fastest ride at this setting.
how/where do you set your saddle height? i was told, as a general rule, put the heel of your foot on the pedal and adjust the height so that your leg is fully extended when you're sitting and the pedal is at the bottom-most of the revolution. at this higher setting, i find myself concentrating on not rocking my hips when i pedal. otoh, i'm faster and more efficient than ever now.