Don't be afraid to get in touch with eBay if you suspect shill bidding - and by get in touch, I mean call them or have them call you. I've done it a few times, and while they can't give specific information, they've more than once confirmed to be that there is suspect bidding on an item, and taken action.

Reporting them through the "report item" link on listings seems to me a completely pointless exercise - have done that for numerous items and never seen any action taken on items reported that way.