Went to Ireland in 2010. Had a great time. Don't do a group tour for all the reasons previously listed. We went in the 'shoulder season' right after the main tourist season. Everything is still open, less crowds. We went the first of September. Bought a package through Dan Dooley, that included airfare, rental ar, and vouchers for B&Bs. Their travel system is based on B&Bs. You set your own pace, stay where you want and have a great time.
The first day of driving on the left side of the road was mind boggling, but you get used to it. For more info PM me.