Vouchers, USD, or Euros When Booking in Ireland?

First the money: get it from an atm - - no room for discussion that this is the best way - - and they're every where. Second the charge: it'll show up on your credit card as X euro with Y dollars charged to you. You'll have something like a two percent foreign tranaction fee tacked on. Third the vouchers: all places don't take them so there'll be limitations; you've also bought the room at a set price. Fourth booking directly: don't bother - - b&b's are everywhere - - you'll have no problems finding one, even at the last minute - - sometimes you'll get ten percent off without even asking, especially if you pay in cash - - the economy has tanked, the Irish are hurting, rooms are not full.

As previously stated, use ATMs to get cash in Ireland. Do not exchanger currency. Always have businesses charge you in their currency, and have the credit card/bank do the exchanging for you (they do this automatically at a better rate and you see the dollar charge on your statement). If have some time before your trip, check to see what your credit card and ATM card will charge for transactions. I use a Capital One card and there is no extra fees and I bank at a credit union who also does not charge me for cash withdrawals and reimburses me for any charges others may place. It would be worth your while to look into this.
Have fun!

It should also be mentioned that you should NOT allow your charges in dollar. It is called dynamic conversion and while it may sound like a convenience for you, it is a bit of a scam. Not illegal but you will receive a marginal if not poor exchange rate and your will still be charge the currency conversion by your credit card company. All transactions should be conducted in the local currency. And, second, always have some idea of what the interbank exchange rate is so you can know if you are being scammed or not.

I used vouchers on my first trip to Ireland, but not since. They can be an incredible deal, no argument there. But I once had a long conversation with a B&B owner (on a non-voucher trip) who said that the owners feel kind of forced to take the vouchers because it's travelers using the great voucher deals that keep their places full in the off-season. The voucher people are very slow in reimbursing the owners for the stays, but they have the expenses of your stay NOW. I have many times gotten just about as good a deal by paying with cash, so I just never used them again.

Thanks for the all the knowledgeable tips everyone.
You've been most helpful in my planning & bugeting process. Slainte!