I bought this Sony Walkman just over a year ago to replace my 1st generation iPod Nano, and I haven't looked to another one since. Here's the ups and downs:

Look and Feel:

This Walkman fits in your hands nicely, and is super light as to not be a burden in your pocket. The buttons are all easy to use, even blindly, with the volume and hold buttons on each side of the player being very prominent and easy to find. I've got the silver/orange version, and it looks pretty neat, the black version looks a little more elegant in my opinion, but I still love this one.


Navigation and Ease of use:

Navigation is pretty simple, with a home screen that shows all the main aspects of the player and the rest being simple to navigate with the up-down-left-right navigation wheel in the middle. The only problem issues i have is that you can't search for any song by simply typing it in, you have to search for just the first letter of the artist or song, which could be annoying if you have 1000s of songs to scroll through. The ipod does trump this walkman in this particular area.
You can however customise the colour scheme and home screen background picture, which is a nice touch.


Audio Quality:

The audio quality is pretty fantastic, with the supplied in ear headphones complimenting it well. The headphones give quality you'd expect with a £50 set, with great bass. My headphones however did stop working after about 6 months, seemed to be something to do wire inside the cable which caused the sound to keep cutting off, so i had to replace them. I'm not sure if this is an issue with all of them but beware of replacing them after a while.


Features:

This player comes with a FM radio, the antenna is built into the player and even so the signal always seems to be fantastic for me. You can save preset radio stations, but that's as far as customability goes.
There's a great features called senses, which analyses all of your songs and places them in category's such a Extreme, Energetic, Acoustic, Classical and a few more. I find this great when I'm going for a run and can't be bothered to make a playlist, or I'm in a particular mood and want the mp3 player to find things for me.
It can also play video clips in wmv. or mp4. format, but the screen is pretty small not of the highest quality, so personally I wouldn't want to watch it for more than a few minutes at a time. It's still doable if you don't mind small screens however, with 16GB flash drive leaving plenty of room for videos.


Software:

The Walkman software is a major let down. It comes across as unnecessarily complicated and difficult to use, and tends to freeze a lot on my computer. itunes is simply better, but you can't sync this walkman with itunes. Instead I use windows media player, which is a lot simpler.
Making playlists can't be done on the mp3 player itself, which would be nice, however you can do this quite easily in windows media player and transfer them.
After syncing the player does have to 'build the library' for a few minutes, so beware of waiting a few minutes if your transferring a lot of songs

Battery Life:

The battery life is fantastic. I only need to charge it once or twice a week with casual use. By turning the brightness down and not playing videos, I'm sure i could get about 10 hours of music play, possibly more. Playing videos will drain it a lot quicker, but even then you could get a good few hours of play.