Security is more important to gamers than ease of use says GoG.com

[Lycanthrope]

Well a decent compromise is to store your CC number but require your CCV to be entered each time, hence you only need to remember 3 digits while still reducing the risk of stolen information.

Would still prefer a box that gives you the option of removing your CC information after purchase than have it stored (with or without the CCV).

There are some sites/services I don't mind storing CC info with (like Steam) but those are few and far between.