I've been on since December. I love it. I don't have a large collection like I once did, but I am enjoying every minute of gradually adding all the cards I do have. I like that I have the ability to change mistakes if I see them, and to add checklists/images if I have the information to contribute, rather than just hope somebody else eventually does it. Having the tool on my collection page that shows, with one click, every card in my collection that is missing an image or a team is incredibly useful. And I am constantly checking my Top 100 baseball players to see who has moved up. I never dreamed John Moses would be so high on my list!
I'm going to reevaluate how I collect after the new year. It's just getting way too expensive for the new stuff. Sometimes I just want to buy a pack, not a whole box or even blaster.