Name an iPhone or iPad app that's much better than any Android or WP alternative.

Just for fun. And to see what you folks are using and relying on that can't be replaced.

For me, it's Marvin. The best Android equivalent is Aldiko, which is sufficient enough to get the job done, but it's not even as good as Stanza before Stanza died. And Aldiko has a completely stupid UI decision where you have to go digging in the Store to get to your Calibre library, which itself is your only option besides USB (whereas Marvin has obvious options for both Calibre and Dropbox, which means I can use Dropbox where my Calibre library is stored :) Marvin surpasses Stanza.

(Screenshot from Marvin site)

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Yours?