Here is an article on this by Jeff Atwood on his "Coding Horror" blog.
http://www.codinghorror.com/blog/2008/03/adventures-in-recha...
I use these all the time in many gadgets. They're easy to find in supermarkets, so it depends where you live I suppose.
Stores have incentive to sell goods that expire fast.
Too expensive, performance degrades over time, you have to have a charger for them and when they run out it takes hours before they're recharged, during which you can't use whatever it is that needed batteries.