With only ~350gh I've yet to get a best share in the billions (been mining about a month), best I've seen was 383M I believe.
I had my block eruptors pull a 30m share, but only do a mil or two now and then... I was really surprised.
610M is my best to date with ~3T. That was running on a local CKPool node. I bounce back and forth between solo.ckpool.org and my local node to see if there is any difference.