There is tons of material online and in the magazines about how the white bundle iPod/iPhone headphones are crap. I was ignoring this quite actively, at first, because I honestly did not notice a great deal of difference between those headphones and several very goo phones I have. At he beginning I was ignoring the difference because I had the microphone on the the Apple headphones. Then I bought Sennheiser’s MM60 and had a relatively good set of headphones with a microphone. The trouble with the MM60 is that although the sound is quite better than the simple Apple headphones they have a whole lot of other issues that for objective reasons or not are making this a bad choice for me: first of all comfort - wearing them makes my ears hurt and I am someone who generally listens on headphones and has had hundreds of pairs and I have to say that even the cheapest sets have never caused me any pain. Then there's the poor quality clip on the microphone and for the price I've paid on those I expected something a bit better. Then I bought the iPhone 3GS and it came with the new headphones with the remote with the volume buttons on it. Loved them from the moment I put them on. Never was impressed by the sound quality, but it was more like when you have a pair of shoes whose look you don't like, but are that comfortable, that you don't have the slightest intention to take them off, ever.
Then came Rodrigo y Gabriela. I discovered them like I think most of the people who are not that much into the independent concerting scene - when they were musical guests of Jay Leno's. After I listened to Hanuman, I bought it in the iTunes store, listened to it the whole next day. That was using Apple's default phones. The next week I spent with the music of Rodrigo y Gabriela almost any musical moment, which is most of my time out of the office and, depending on what I am working on, even a part of my office time. And I once have tried a cheap but good headset - the MDR-V150 - it is acoustically the strict opposite of small headphones - giving a powerful and profound bass an cutting a bit on the highs. This is a very good feature for me, because highs give me nasty headaches and my long years as a head-banger has left me with a certain soft spot for strong basses.
Now I have a new tech purchase aim, after I buy my iPad, of course (but this is a whole other theme and a huge one at that) - finding and buying a very good - meaning not bad audio quality and good wearing comfort for a reasonable price.