It's rare there is such great news for open geospatial data. Here's the "Welcome, Apple!" entry from the OpenStreetMap Foundation. Of course there are initial quirks, but it's a start and it's excellent pushing in favor of OpenStreetMap data.
From the welcome message: "The desktop version of iPhoto, and indeed all of Apple’s iOS apps until now, use Google Maps. The new iPhoto for iOS, however, uses Apple’s own map tiles – made from OpenStreetMap data (outside the US). [...] The OSM data that Apple is using is rather old (start of April 2010) so don’t expect to see your latest and greatest updates on there. It’s also missing the necessary credit to OpenStreetMap’s contributors; we look forward to working with Apple to get that on there."
Of course, Slashdot is also discussing the news and MacRumors provides more insights: "Daring Fireball's John Gruber later clarified that Apple was still using Google Maps for the Places functionality in iPhoto for iOS but that maps for Photo Journals and slideshows were coming directly from Apple. [...] Toward that end, Apple has been working hard to beef up its own in-house mapping expertise over the past several years, acquiring several small companies including Placebase, Poly9 and C3 Technologies."
For the U.S., Apple is apparently using TIGER data. If you're curious, here's a nice tool to compare Apple tiles (based on OSM) and OpenStreetMap tiles. If you're eager for more coverage from the generic web sources, APB offers more links.