I am truly undecided at the moment about my mattress protector.  On one hand, in a house with pets...and a propensity to drink coffee in bed...I like the idea of having my Casper Wave protected.  It somehow feels that the addition of the mattress protector significantly increases the firmness of the bed.  as a back and side sleeper I like a medium firm mattress.  I probably find the mattress more to my liking (in terms of comfort) without the protector.  That said...the protector is on.