I have never been a fan of running while having an ipod or mp3 player stuck to my arm. I have been very impressed with some of the wireless solutions on the market. I currently use a Solo wireless mp3 player which has out performed the other 2 wireless units I have by a long shot. I'll pay a few dollars more for wireless and better quality. My Solo can handle any music format plus audiobooks ( which my wife loves ) The other 2 wireless units I have work ok but the sound quality doesnt match that of the Solo. Sound quality might be important if you listen to certain style of music but my wife says that sound quality is very important when listening to an audiobook. Hope this helps! Here is a link the the Solo if you want to check it out.
Solo Wireless Digital MP3 Player