From July, the Prize Bonds prize structure changes. The number of €1m prizes has been reduced from six to four, and the €100 prizes have been replaced by a much smaller number of €500 prizes. That is the good part of the news about these changes, since a reduction in large prizes increases the proportion of the fund paid out in €50 prizes. Furthermore, the total amount invested in Prize Bonds (which also affects payouts) has increased from €2.3bn at the time of the last prize structure change in October 2014 to €2.6bn now.
Unfortunately the fraction of the fund paid out annually in prizes is changing from 1.25% to 0.85%. Taking all the changes into consideration, the average weekly number of €50 prizes will change from 7,200 to 5,700. And your chance of winning them goes down too, due to the 12% or so more prize bonds on issue.
In summary, the average return for an investor of €100k will fall from 0.81% to 0.58% tax free. Grossed up to the equivalent rate on a deposit account incurring DIRT, this is a fall from 1.5% to 1.0%.
Since rates have been dropping everywhere it's still ahead of most of the deposit products out there, but for me not worth the administrative hassle.