The pricing is perfect, considering that this is a universal application for both iPhone and iPad. Although I will admit that the iPad option wasn't really thought out, that this application was really designed for the held-held iPhone or iPod Touch. Some clues: this application doesn't do landscape and images are still pretty tiny, with no option to expand to a larger version. The larger images isn't going to be deal breaker, in fact, I can understand why they'd want small images, because I'm assuming there are about 365 images (which could explain why the application is a large 90mb download). I do like that the images are randomly displayed.
As for the meat of the product, you get a trivia about Led Zeppelin based on the day, broken down by various years. For instance, this day in Zeppelin (January 31st), LZ played their first of two nights at the Fillmore East in New York in 1969 and in 1975 they played Detroit Michigan (with the set list information). The nice thing about this is that you can skip around, so if a particular day is important to you (like, say, your birthday), you can read what LZ were up to that day.
As I previously mentioned, some of this data is a little far-fetched, like do I really need to know the birthday of Deborah Bonham (sister of the late drummer John Bonham)?
But wait, there's more, you get a few extras with this application: Trivia, Quiz, Song Notes, Store and Extras. The later two will take you out of the application, so I'll just only briefly mention the first three. The Trivia are basically recycled data from the "On this Day" information, I think in random order. The Quiz is fun, you aren't told what the right answer is and it's only in session of 10 questions per quiz (also random questions). The highlight is the Song Notes for me. Much more information than any liner notes, this drills down from album details to facts about each song. Of course, I looked up "Stairway to Heaven", which is their most popular song in the US (despite having never been issued a single in the states). The song was so popular that it was played on terrestial radio over three million times. Just to put that in perspective, they said that if you played all three million back-to-back, it would run for 44 solid years.
Anyway, a delightful program, This Day In Led Zeppelin is recommended if you like Led Zeppelin. It is doing well in the iTunes UK and I'm holding out for a This Day in The Smiths.