I purchased the E454B to replace my rather battered Archos 3 Vision.
Firstly, battery life can only be described as exceptional. I tend to use mine at work and I only charge once a week.
The screen quality is really good too - sharp, clear and flicker-free on video playback.
Audio quality is the slight letdown on the Sony, there is no bass boost feature (though I compensated for this with bass-enhancing headphones). On the upside, there's a good selection of equalizer settings with a couple of slots to define your own. Volume is somewhat quieter than other players I've had, but using a quality set of headphones seems to overcome most problems.
Video quality is great, no problems at all with the .mp4 format, and it's possible to squeeze video into some pretty small file sizes. I can currently get two hours of video into 375Mb without loss of quality.
The controls feel solid and are generally well placed, but might be a little sensitive to some. The menu options seem to work well too, it's not too hard to find what you're looking for.
The E454B has some interesting extras for audio playback. The Mood feature can analyze your collection and determine what type of music it is - Calm, Energetic, Dance, Lounge, etc. I was dubious at first, but it seems to work surprisingly well.
Clear Audio seems to add an extra layer of quality control to your audio. It's not perfect, sometimes you can lose some sounds in a track, but the overall experience is good.
My only real gripe, apart from the audio, is the strength of the screen. It would have been nice to see a scratch-resistant screen on this player. I purchased a leather cover for the player to compensate.
Overall, a great player with some decent sound quality, fun features, and an incredible battery life, only let down by the missing bass boost and weak screen build.