I didn't put a "beware" in the title, as that would seem ominous.
However, anyone buying a Maxroam SIM should be aware that the Ryanair version and the version sold on the Maxroam wesbite have very different rates.
The rates for the SIM sold on the Maxroam website can be found here:
Rates Page
The rates for the card sold by Ryanair can be found here:
Rates Page
In essence, the Ryanair version has cheaper rates calling within the EU without using callback (29 cents vs. 39 cents.) However, the rates to call outside the EU, even from within the EU, are much higher. For example, calling from France to the US is 49 cents on the Maxroam site version (39 cents using callback), while the same call using the Ryanair version is 99 cents (no callback option.)
There is also a difference in the buy-in price. The Ryanair version can be bought for 5 EUR with a 10 EUR credit on the SIM, while the cheapest buy-in on the Maxroam site is 15 EUR, with 10 EUR credit on the SIM.
Depending on the intended use one card would be better than the other.
While the rates to call North America are far cheaper on the Maxroam non-Ryanair version, one option might be to use the Ryanair version with its cheap EU calling and combine it with a Betamax type access number with free calls to the US. However, under that scenario one would be charged starting with the call being answered by the Betamax number, not the ultimate number being called.