the new classic is manufactured in a way that you need a hammer drill or a nuclear weapon to open the case and any DIY effort will destroy the machine completely.

Battery life: I assume that if you listen in the car, you're not worried about battery life. Surely if you're constantly streaming, the battery would be caned. Is that what you've found? - I'm off to GiffGaff as soon as my contract with the rotten Orange is up and planning to stream from my NAS drive but I'm assuming that it won't replace an ipod for all day, mobile use.
Compression: What standard do you have your files stored in? Obviously the higher the compression, the smaller the file and the less strain on the network.

I have a 32GB Creative Zen. Love it for the extra capacity over the old 20GB iRiver and the SD slot was one reason I chose it. A pleasant surprise to find it read SDHC cards, which were new-ish at the time and not every SD-capable device would read them.

The drawback to the SD card is that the player doesn't remember where you were when you use it. If you are listening to the main drive and power off then when you power back on it starts where you left off. If you were listening to the card you have to start from scratch which is a pain because I use it, like you, for podcasts. A real pain if you are trying to listen to a series of them in order.

I still wouldn't swap it for anything else though.

but apparently it doesn't work in Windows 7 64 bit so unless they can fix it with some new firmware that's no good to me.

Everybody rates the sound quality but there appear to be niggles around battery, interface, screen and ease of use. And most people seem to like it because they use flac. Seems to be the ideal player for a particular type of user.

I think the problem is the EU volume cap on iPods as discussed below. Don't need it blasting out but nice to have some headroom. I also miss the graphic EQ I had on the old iRiver.

I bought a Sony Walkman in the sales recently which is very quiet, so it's not just an Apple thing, but checking up on the internet it appears there's volume limiting on UK models, and not just in the user settings. I can just about power a pair of full-size Technics 'phones, but at very low volume. Sometimes there are hacks available to improve output, but I've no idea if this applies to iPods too.

or australia or another jurisdiction without the limiter law ?

The ipod continued to increase in capacity until Sept 2007 when it stopped at 160G for the classic (still short of enough to fit everything on) and the 16G nano didn't appear for another year. I think the thing is, once you've accepted that you can't carry all your stuff in one ipod, 16G is just about enough... although had they brought out a higher capacity nano I would have got one by now, just to give me a bit more headroom.
Note, the biggest MP3 sellers are still ipods and you can't watch video on the current nanos.

... will tell you this is part of the Grand Plan to get everyone into The Cloud, by halting development of ever bigger memories, and sticking to the smaller capacity models.

On the other hand, bearing in mind that apparently the average UK household record collection is less than 40 albums, <10MB is clearly enough for most "civilians"...

is 64GB so there are options above 16GB.

I can't get all my music on it though so it is too small to carry my collection around. However, carrying my entire collection around is mostly impractical. Filling it up with music makes it tricky to use in my car. Whilst my car has a snazzy interface that lets me scroll through the artists, having several hundred artists to scroll through in the car is a real pain and hardly a major contribution to road safety. So I tend to only keep favourites, play lists and recent stuff on it.

the hard disk drives inside the original iPod and the first generation of mp3 players (i.e those with moving parts and an actual spinning disk inside) are just too unreliable and fragile hence my iPod is knackered after just 4 years of use.

Apart from the iPod Classic and the Cowon model, all mp3 players are now based on solid state drives (like a memory stick), and at the moment 32GB seems to be the maximum that can be provided without the device becoming ridiculously expensive.

The other reason is that a lot of people now prefer to use their smartphone to listen to music instead of carrying around a separate mp3 player. People are happy to trade off that extra storage space for the convenience of having one device that does all.

Personally, I still prefer to have a separate device for music not least because of the battery life issue with most smartphones. If I'm on a long train journey I want to be able to listen to music without running the battery down on my mobile phone.

It does feel like the market has withdrawn from the high capacity hard drive based mp3 players rather too quickly, but I think what this has done is made your average consumer realise they don't need all that storage, so people like me who love the idea of carrying around the entire back catalogue of The Fall plus 100s of other LPs are in the minority.