I was listening some podcast today and someone said it well; Start-ups build apps, use us to figure out if there is any traction (guinean pigs) and then those apps ends up being features on something more valuable.
I think the trigger to that conversation was this years SXSW hit app Localmind. Podcast host argued that Localmind should just be a feature on Yelp's app.
I use surprisingly few apps. Here are the most important ones (in a order of importance):
iPhone:
1. Facebook
2. Echofon Pro (UberMedia app)
3. Foursquare
4. Runkeeper
5. Instagram
And then I, of course, use iPod app tons as I love to listen tech podcasts
Nexus S (Android):
1. Facebook
2. Twidroyd (UberMedia app)
3. Foursquare
4. Spotify
5. Google News
Interestingly I don't use Runkeeper on Twitroyd as Android's podcasting listening apps are not that great so I cannot use my Nexus S on running and mountain biking.
Also on Android, I like Skype and Google Sky Map that enables me to see which start is which on clear night sky.
So, other than these apps, no other apps have really stucked with me. I try new apps every week, but my favorites remains the same.
Importantly, I do believe on paid apps and whenever paid "pro" version is available, I tend to buy it. Samples of apps where I have been happy to pay for premium version: Runkeeper, Echofon Pro, Spotify and Angry Birds.