hi weshtraveller - your message re the vouchers.. my experience is ..
Aer Arann ran this last year and i ordered vouchers. I've had the vouchers all year and in late November I phoned the call centre and booked flights for 9th Dec. I got the flights at the published online rates. Literally I looked the flights up online that i wanted, noted the flight nos etc and called the booking line.
There wasn't a catch - i.e. something bad or dodgy as far as I could tell, other than you have 1) to use the vouchers within 1 calendar year and 2) to phone the reservation line (rather than book online) - which was busy for about 20 mins, on a sunday, without an indication of where i was in a queue. BUT having said that, the lady that answered was really friendly, and she emailed my booking details to me.
Bottom line, I have a few days until I fly on my first vouchers, but when I saw the offer again, I ordered new vouchers for next year as it was so easy to do before.