I have a Sony Ericsson W910i, which can take a 4gb m2 card. In the box is a 1gb card, headphone dongle, a pair of Sony earbuds, a usb cable that doubles as a very portable charger, and a usb stick adaptor thing for the m2 card. I often use it with my new Super.fi 5 Pro's when commuting.
Positives:
The sound quality is pretty good, certainly holds up to my old Network Walkman, and it's a very pretty gadget. You can create playlists on the fly and drag and drop files (no Sonicstage nonsense) with either the usb cable/charger or the m2 adaptor. You can just about skip tracks and change volume with the phone in your pocket.
Battery life is good, and I use it day to day without too much hassle.
Negatives:
Biggest flaw is the omission of a 3.5mm socket.
You are forced to use the dongle, which leaves you with loads of cable to tuck away when using any other headphones (the included ones are designed to connect to the dongle close to your neck, and have a very short lead). The dongle sticks out of the side of the phone, which means you can easily disconnect it when taking the phone out of your pocket.
Doesn't feel as solid as other phones I've had (has a slider mechanism).
Can be a little fiddly to use, but the new Walkman software miles ahead of most other music phones I've seen (though not up to iPhone standards I'm sure).
I'm no good at writing reviews, but in general I think the w910i is excellent, it's such a shame about the socket thing.