I have multiple magazine subscriptions across the varied app's available (Newsstand, Zinio, stand-alones, etc.) and find Boat International to be plagued with some issues.
While not National Geographic, there is plenty of interactive content to make each issue an upgraded digital version of the print magazine. The Zoom feature is better than most, and combined with the ability to see the featured photos as a gallery make detailed observations of the vessels a snap. Each issue is large (think Wired) so expect a chunk of download time.
The problems began, for me, with "Updating the Shelf". Seemingly an endless process, I have resorted to doing a full iPad turn off/on to simply read the magazine in a reasonable time. I don't know if it's related to the NISI video played at start-up, but it's annoying at best.
Clearly the defect is the application, not the content of the magazine. I'm surprised frankly, that a publication intended to appeal to the most discriminating of readership would allow its digital "face" to be so poorly received.
Here's to hoping an update will right this ship.