| I have an iPod 4g 20Gb that I bought last June. I hated it and regretted buying it within a couple of hours. iTunes is inflexible and the MP3 format leaves a lot to be desired from a high fidelity point of view. Even the Apple Lossless and other supposedly lossless formats are dynamically limited and have high distortion compared to CD. I tried it in with my stuff at home and it is easily bettered by any of my other sources, including cassette and FM. This is probably poor quality op amps in the iPod adding to the misery of the MP3. For cheap headphone use or in car ipod is acceptible.
The battery duration is claimed to be 7-8 hours. This may be possible on the very lowest resolution MP3s if you never skip tracks. You see the iPod reads as much as it can into memory and plays that. On low resolution MP3 it may read 20 minutes of data at a time. Once the resolution goes up it may only be able to store 1 minute or so. Therefore the disc is either constantly running or stopping and starting all the time. My best run time is about 5 hours. Battery life is also poor. I have not had to replace mine but I understand that after about 15-18 months the battery dies and has to be replaced, not cheap either! When my battery dies I will not bother to replace it I will just use the adaptors or maybe just use it as an external hard drive for backing up files.
I wish I had bought the latest minidisc recorder instead. The latest ATRAC versions are capable of recording at higher than CD quality. If MP3s are really your bag then each optical disc can store up to 1GB. Best of all it takes one standard "AA" battery, replaceable anywhere.
As for the Mini, I use MP3 discs. Cheap and simple to make and use and avoids the poor quality op amps of the iPod. If I could just plug my iPod straight into the car I would probably use it but I certainly would not pay more than beer money to have it installed. From a sound quality point of view it is just not worth it.
Of course this is just my view. If you really want the convienience and annoyance of trolling through so many songs to find the one you want (once you have 1000 songs on there it is not easy) then go for it.  | 
