A few things about Elixirs...
The original Elixir strings were their "Polyweb" coated models. Basically the string is encased in a thin plastic tube that helps prevent the string from corroding. Because this tube can deaden the sound significantly, Elixir compensated for this by using 80/20 bronze, which is significantly brighter than the usual phosphor bronze that is more commonly used on acoustic guitars. Even so, many players don't care for the tone of these strings.
Elixir eventually improved upon their design and released their "Nanoweb" coated strings. This just means the plastic tube is much thinner, and impacts the tone much less than the Polyweb strings. Unlike the Polyweb, the Nanoweb strings are available in both 80/20 and phosphor bronze.
Personally, I love the phosphor bronze Nanoweb Elixirs. It's not that they last a long time -- if you play the guitar a lot, then you won't get significantly more life out of them than you would other strings. What they excel at is keeping the strings fresh when the guitar isn't being played. Sometimes I go for long stretches without really playing my acoustic, and the Elixirs do a good job of keeping the strings from dulling and corroding when the guitar is just sitting on its stand. I used to hate how I'd restring the guitar and then three weeks later the strings were disgusting, when I hadn't even touched it. Elixir Nanowebs solved that problem for me.
I normally use a light set, but Elixir just announced a new "
HD Light" set that has the bottom three strings from a light set, the top two strings from a medium set, and a wound g string that's in between the two. They make a big deal about it supposedly evening out string tension. They're supposed to be released next month, and I will definitely try these out.
All that said... I find myself agreeing with LSchefman about an awful lot of things around here, so if he recommends the D'addario Bluegrass set, then I'll probably try those out as well.