I'd love to hear specifics.
iOS Google Maps hit at just the right time with just the right amount of UX and visual design. I've just moved to Pittsburgh for the year, and I depend on some sort of mobile transit app to get around town. When I updated to the newest iOS, I had to use applications that had nowhere near the fidelity of transit data that Google had (and it made me late for classes, meetings, and had me stranded in the cold several times).
The real joy was that I got turn-by-turn on my iPhone 4. For years I was deprived of this by Apple. It was an incredibly pleasant surprise.
+1. So very well done.
I love the new seamless app (use of color, fonts, great contrast).
Rdio for iOS is fairly nice. The design is clean and the functionality really compliments it. Recently bumped up my subscription for them, so I can really take advantage of it on my iPhone 5.
I've found it's super easy to get around to browse your music and others, as well. They keep it all super simple, that's what I love the most.
National Parks by National Geographic, Google Maps, and Flipboard.
Clear :) it's a joy to use — it tricks me into getting more done as I want to play with the menu system/hear those lovely sounds
The Simple bank iOS app is beautiful. I sometimes just open it up to look at the design and nothing else.
Path, Clear and Evernote. Especially Path. The more I use it, the more I realise how much effort and thinking must've gone into it.