Just got a new E5 and the button seems a little stiff (harder to push in) compared to my others (mostly quantums).  Is this normal or do I just need to break it in?

Button should not be hard to push at all.  I would ask this question over in the Shimano support forums and ask Bantam1.  He will be able to give you all the help you need.

Later,

Exchange the reel for another.

A new Curado should be good-to-go

right out of the box.  

8-)

Just got a new E5 and the button seems a little stiff (harder to push in) compared to my others (mostly quantums).  Is this normal or do I just need to break it in?

Don't mess with the reel....While Quantum® reels aren't built as tight as the Shimano® reels are..

Return the reel immediately to where you purchased it for a return/exchange or refund..

When you do, if your standing at a counter take the reel out of the box and give it a once over, but i'll bet you purchased this reel from an on-line store.....

As SW mentioned that reel should be smooth and work freely right out of the box...

Good Luck & Tight Lines!!!!