Here's a link to the official memo from ebay:
http://www2.ebay.com/aw/core/200701081004422.html
Good points:
(1) It will be a lot more difficult for people who intentionally follow my bidding and try to outbid me to do so.
(2) It's more like a silent bidding auction where everyone shows their cards at the end and the high bidder wins.
Bad points:
(1) Lower overall final prices since if I know that a certain person is bidding on this card, I will automatically increase the amount that I would otherwise be willing to pay (with several cards from a set, i.e. PSA 6 C56's from 2-3 years ago, PSA 3/4 C57's from 1 year ago, I knew that I would have to dig deeper to win any of those)
(2) Shill bidding is even easier to do since following the bidding patterns of Bidder A vs. B vs. etc. is more time-consuming
Remember that this only comes into effect at $200 and above. The winning bidder is still revealed. For me, I don't know yet if it will change my bidding habits or not.