Which Pay-As-You-Go provider can you recommend for a tourist?

A German friend is visiting me for one month and I want him to get a good plan for the time of his stay. I had experience with Rogers pay-as-you-go, but was very dissatisfied with the service and tariff. It should be easy to register, top-up and shouldn't involve this outrageous policy, that one has to top-up the credit after a specific time, or otherwise the full credit would be reset. (This policy reminds me of the beginnings of mobile telecommunication services many years ago...)