I use all premium fly lines and I don't really have any problems with line memory. The lines might have a little memory if I haven't used them in a few months, but it quickly disappears after a little casting.
The tapered leaders show more memory, but I've found that using large arbor reels limits this quite a bit. But it's still there and can be frustrating sometimes! One big thing I've noticed is the leaders get a lot more memory if they're stretched tight around the spool during storage. Leave them on the spool loose and they do a lot better.
My passion for catching fish is eclipsed only by the fish's passion not to be caught.