I haven't known that app yet. Thanks for informing
I just downloaded and tested the app.
I think there's just one reason of using this app: offline routing service, so you save money for roaming costs.
But I do not believe it will replace the Timetable book, because you do not know, which place are directly connected or if there are any night trains. I think a railcc App would be nice, because here you find all information, you need for railing
but there's also a pdf version of the book, which can be used on tablets or smartphones as well: eurail.com/sites/all/files/eurail.com/downloads/2013/eurail_timetable_2013.pdf