When I first got my I phone 3G (2 years ago) I spent a great deal of time downloading apps, not using them and ultimately deleting them. I ended up with a core (a still ridiculous 60 or so) which I kept.
A month and a half ago I got my iPhone 4S. I spent a great deal of time downloading apps (again). The advances in technology (through the iPhone 3GS and 4) means that the phone and the apps work together in a way they didn't before. I deleted a lot of the new ones; but I also re-discovered some old ones which work better than ever before with the latest operating system.
A while ago I was taken with two amazing bright 'stars' in the early evening sky. My 'Planets' app told me that these weren't in fact stars but the planets Jupiter and Venus. It could even turn in the direction I was looking!
So now every so often I turn my eyes skywards once the sun has gone down and see what is in the sky. The app tellls me the constellations; of course if I want the names of the individual stars then I'll need another app!