All the information I have at the moment is that the euro introduction has been a great success in Slovenia and the preparation which has been done by the central bank and the government as well as the ECB and the European Commission, has been very careful. To my knowledge, the success includes efficiently limiting and avoiding abnormal price increases.
I don't think the long period of double pricing should make the estimate more difficult. I think it was a good idea to have a long period. BIS Review 32/2007  5