After a while the pedals do get a little harder to get in and out of - even when you they can be a pain in the ass...
The speedplay teflon lube is your friend.
Clean your cleats and pedals very well, dry them and lube the cleats and metal parts on the front/back of the pedals. Let the lube dry for a minute and enjoy very slick operation...
If you tighten the cleat screws too much then it will be very hard to get into and out of the pedals. "Just enough" is all you need to tighten them - and that really isn't a lot. Remember to use threadlocker (loctite blue) on the screw threads to help stop them come loose.