The default Android calendar app is nice. Not amazing, but definitely more usable than the iOS calendar.
The notes app on the G4 seems ok, but saves its notes to a hidden folder in Google Drive. This fills me with fear for the time I want to migrate to a new notes application. I want to be able to see my backups in plain text somewhere so I can reuse them - migrating from Apple to Android has really shown me the benefit of thinking about that up front. iOS notes was sync'ing to GMail and I wanted something which would do the same. It took some searching, but I turned up GNotes which not only syncs in the same way, but when I gave it access to my Google account pulled all my old iOS notes through. Impressive. At some point I will have a look at Google Keep, but this has got me started.
Shazam seems slightly better designed on Android, although that could be my imagination. Annoyingly (but not surprisingly) I had to buy the ad-free upgrade again. I was hoping it would let me log in cross-platform to avoid that repeat charge, but alas not.
Having Chrome on my phone is lovely. Rather than messing around with bookmarks in Safari they are just sync'd from my desktop. I could have done this on the iPhone of course.
Mailbox isn't quite as nice as the iOS version. Functionality is the same, but I keep opening mail when I am trying to swipe - something I don't remember doing before. It's still by far the best mail app I've used though.
Textra is a great text message app. Not much more to say on this except that I've coupled it with SMS Backup+ which is sync'ing my text messages with GMail to avoid the horror experienced when trying to save them in a readable format from iOS.
The Flickr app. Hmm. Photo uploading was always going to be a big difference between the two operating systems because it demonstrates a major difference in the underlying ideology. In iOS to upload to Flickr you fire up the Flickr app, select your photo, edit it and upload - it starts from the application to upload. In Android you start from the picture, open it in the editing program of choice and push it to another app to handle the uploading. The change takes a little getting used to (change is change, even though the Android setup makes a lot more sense) and would be much better except for one important fact - the Android Flickr app is awful. Significantly worse than the iOS version. It seems to be missing several key features for editing (auto-correct, most of the effects) which makes it only useful for uploading and unless you want to post to Twitter at the same time, the Bot for Flickr is actually a better option for uploading as you can queue a load of pictures to automatically upload next time you connect to a wifi connection.
Photo uploading also highlights a security feature in Android which hasn't fully been adopted by the app developers yet. Resources on the SD card from one application cannot be modified by another application unless permission is given. When you take a photo, the image is a resource owned by the camera so you can't modify it with an editing application. Instead, the editor needs to save a copy but the apps I've used do not switch to this new version on save so I've had to edit, save, back out of the picture, and go into a different picture stream in order to find the saved file for uploading. There is some explanation of the underlying problem in this thread.
The upshot is that uploading photos involves an annoyingly convoluted workflow. It's not the end of the world, but could definitely be better and this is using the (otherwise excellent) Android / LG gallery app.
So far, I'd say none of the apps seem different enough to make a huge difference to anyone's life. I was surprised how easy it was to switch between operating systems and either keep the same apps or find easy substitutions.