I've had an iPod for over 20 months and it still works fine. In fact I have bought another one!
If there is a battery failure there is a replacement option, however it is a little expensive.
As for iRivers player, yes, it has a lot of versatility, and was designed and built long after the iPod first arrived. So they already had a benchmark to compete against.
Any manufacturer bringing out a new device can supercede similar devices.
Perhaps Apple will bring out a forth generation iPod.
As it is, one can attach modules to iPods that allow it to be used as an FM radio, a dictaphone, a short range transmitter for its content, a store for your digital media files like camera memory cards, has a built in calendar and address book that sync's with your computer, can be used to transfer files from computer to computer using high speed FireWire IEEE 1394 protocols, Can hold about 8000 3 minute songs at 160kps which sounds as good as any CD player, unless you are of course of perfect hearing. It even has a few games you can play on it. There is also a infrared remote control available for it.
For my money the iPod is still the best buy for portable MP3 Players.