In no particular order:
If for no other reason than I could claim back the hours and hours spent downloading stuff over dial up!
Of course, there are innumerable things it has enabled us to do apart from faster downloads. Cloud computing became practical, watching TV on the web, web apps became a viable alternative to traditional desktop apps to name but a few.
This has become indispensable to me over the past 2-3 years. It would be fascinating to have a large chunk of a lifetimes data sitting in there, looking back, seeing how my priorities, dreams, desires etc have changed over 30 years.
Simply the best overall piece of kit I've ever owned. Nearly 4 years old now, but as good as new, and nothing makes me even want to consider replacing it. When it does give up the ghost, I'm sure you can guess what I'll replace it with.
Given that 30 years ago I was in a world of Sinclair Spectrums etc, I couldn't even imagine back then that this sort of portable powerhouse would even be in existence in my lifetime.
I've only had this a few days (having been a dedicated user of the iPhone and Android apps for some time), but already can't imagine being without it.
I always have 3 to 4 books on the go at once, plus a number I like to use for reference. Being away from home a lot, it's fantastic not having to lug all that weight around all the time. Combine that with synching across devices (I can read a little on my Mac, or my Dell Streak and the Kindle knows where I've left off on every device) and it's just about perfect. Plus, it makes my wife happy, as I can now clear out a lot of those space consuming "real" books at home!
Being a cheap skate, I'm always on the lookout for bargains. I've discovered some real gems around the Net that I probably would never have found without the Kindle/Kindle apps, so it's also a terrific discovery engine.
A rather obvious one, but it has to go on the list.
I can't even begin to imagine how many photographs I've lost over the years, for a variety of reasons. Having it all digital, and backed up in multiple places, means I never have to lose anything again (I figure losing the data from 5 different sources is going to take some doing).
Additionally, you don't have to worry about the cost of processing, which means I can take as many shots as I like and hopefully get a few good ones worth keeping!
Over to you
What would be your top 5?