Just bought my iPod mini Silver on Monday, it totally kicks. The iTunes integration is very nicely done in my opinion. Yes I'm disappointed at the price/storage ratio but as far as it being a portable audio device, nothing can touch it for ease of use.
As the others have said, it's charged in one of two ways: The included AC adapter uses the Firewire cable to charge the iPod from a wall socket; or you can use either the Firewire cable or the USB cable attached to a PC. Mind you, the port you're plugging into on the PC needs to be a powered Firewire/USB port. Not all of them are automatically. If you have a keyboard of some kind with a USB port in it that most likely isn't a powered USB port; most of the time USB ports directly on a computer case or motherboard tend to be the powered ports. I'm not a big fan of Firewire because of it's non-widespread use on PCs (I can find USB on any PC but the same can't be said of Firewire, although it is becoming more common).
Unlike all the other iPods, the mini comes with a Firewire AND a USB cable so you can use either one based on what ports your PC has.
As far as transfer speeds go, don't buy into the BS that people will preach about Firewire being faster, USB slower, etc. The 4GB hard drive inside the iPod mini can't write data at more than maybe 3MB/s anyway, so being able to transfer songs from the PC to the iPod at over 30-40MB/s is pointless since the iPod chokes when trying to write the files to the hard drive. Kinda like attaching a fire hose to a garden hose: The pressure and amount of water flowing through the fire hose can't possible fit in the garden hose so you'll be throttled down to the garden hose speed/flowrate. Same principle, I just can't think of a better way to explain it.
With good earplugs/earphones/headphones I'd say the iPod mini sounds fine. I think people spend to much time complaining and worrying about "CD quality" with regards to these portable audio players - but that's just my opinion. If I wanted true CD quality I'd have bought a real PCDP (Portable CD Player) instead of an iPod. With AAC at 192Kbps encoded with iTunes directly from the original CD, I'd say anyone short of a professional audio recording engineer (or Commander Data from Star Trek: The Next Generation) would be hard pressed to complain
As for build quality, it's awesome. A nice solid piece of equipment. You begin to appreciate it as a true work of art once you have it for a few days, it's just beautiful design and engineering coupled with very easy usability.
Hope this helps,
br0adband