Two Thoughts
DEW:
I thought the MegaBus used the same airfoil-section as the A-320; just more of it. But, if they used an airfoil-profile that is thinner (increased fine-ness ratio) in order to achieve higher critical Mach numbers, then pitch would have to increase more in magnitude to achieve a different Coefficient of Lift than what you are used to.
From your original post, though, I wasn't sure if you are talking about magnitude, or rate of pitch change.
The second thought: where were you in relation to the center of lift? If you were near the tail or nose (maximum length of moment-arm from the center of lift), you are going to feel a lot of up-and-down motion for even small pitch changes. I'm guessing on fuselage dimensions, but I would guess you could be 100 ft aft of the center of lift in the back of the plane, and 75-ish if you were in first-class.
Those moment-arms are double to triple that of the A-320.