The iAudio U2 1 GB Digital Music Player was the first true MP3 player I bought. I did a lot of research prior to buying it and I was very pleased with it the entire time I was using it.
The standout features of the iAudio U2 that originally attracted me to it were the long, rechargable, battery life (20 hours), good sized lighted LCD display, small physical size, and no third party software requirement.
The iAudio U2 has 1 GB of storage, FM tuner, and voice recording, all pretty standard features on MP3 players then and now. It comes with a protective leather & plastic case and lanyard. It is quite ideal for hanging around the neck -- something that looks really stupid with larger MP3 players. It will play MP3s, WAVs, and WMAs. Also in the package is JetAudio software which, while a bit clunky, is still an application I use to rip CDs.
The iAudio U2 connects to the computer via USB and you can drag & drop files onto it, whether they are music or data (though it will obviously only play music files). This is nice because it means you don't have to deal with any third party software to load it and you can use it as a regular flash storage drive if you need to move some files. The menus on the player are easy to navigate and the backlight/scrolling speed are all configurable. Additionally there are some preset equalizers and bass boosting effects that work quite nicely.
I used mine a lot, usually at least an hour a day, sometimes up to 5 or 6, for two years and the battery still keeps an almost 10 hour charge. If you did need to replace the battery, it is not an easy thing to do, and you'd probably need to send it back to Cowon. I have no complaints about the player at all, it always performed well, even if it is a bit dated now.
If you need a small player that can take a beating, isn't complicated to use, and has great battery life, this is still a great buy especially if you can get a good deal on it. The only reason I upgraded to a different MP3 player is because I wanted one with Rockbox support.