It's been awhile since I update the
audiophile hobby of mine here, but today I've been very excited since getting updates of the new Sony Walkman music players via the subscribed RSS feeds.
First off, the mid-end S series,
S640 & S740.
S640

S740
Screen: 2.0" LCD (TV output at 720×480 (SD) resolution available)
Storage: 8GB, 16GB & 32GB (S740 only) flash memory.
Earphone: MDR-EX300SL (S740's earphone is similar to MDR-NC33)
Sound Enhancement: Noise-cancelling (S740 only), Clear Bass, Clear Stereo, and DSEE.
Functions: FM Radio, ability to display lyrics (might be limited to Japan models only), play speed control
Battery life: 42 hours music playback. 10 hours video playback.
Codec:
Music -MP3, WMA, AAC, HE-AAC, ATRAC, ATRAC AL, PCM/wav.
Video - AVC (H2.64), MPEG-4, WMV.
The difference between the S640 & S740 is the design of the player (S640's plasticky feel while S740's metallic feel), the noise-cancelling function (exclusive for S740), the earphone and the 32GB which is exclusive to S740.

I had the previous generation
S730 series, and still using it now. Quite happy to see the improvement in the hardware and quality, but sad to see the demise of the auto playlist SensMe Channels.
Next up, the higher-end version A series,
A840.

2.8 inch WQVGA OLED screen (with TV output function at 720X480 resolution)
Slim design with the thickness of 7.2mm.
Storage: 16GB, 32GB, 64GB
Sound Enhancement: S-Master digital amplifier, Digital Noise Cancelling, DSEE, Clear Stereo, Clear bass, and lyric display.
Earphone: MDR-EX300SL (with NC function, similar to MDR-NC33)
Battery life: 29 hours audio listening. 9 hours of video playback
Codec:
Music - MP3, WMA, AAC, HE-AAC, ATRAC, ATRAC AL, PCM/wav.
Video - AVC (H2.64), MPEG-4, WMV.
Another fine piece of gadget by Sony, this is the new flagship model which I believe will get along together with the current flagship touchscreen
X series.
I'm kinda interested to know which would sounded better, though I'm slightly biased towards the A series due to it's better earphone, the MDR-EX300SL.

The new S series & A series is likely to be available by November. Still don't have much idea bout the pricing but I guess there's a price to pay if you wanna enjoy high quality music.
For me, I'm actually tempted to get the A series in the future. Love the sound of the current player, but A series will definitely sounded better as it comes with the S-Master Digital Amp that builds in within the player itself. Besides, I love the noise-cancelling function too, glad it didn't been taken away heh.
A 16GB is not enough for me, so I'm likely to get 32GB or 64GB model. Budget budget, hmm.....
Left to right: A840, S640, S740, S730.

Anyway on to give my advice whether you should get the new Walkman players or not, do take a few points into consideration:
- It performs superb in music-playback but doesn't comes with fancy application like those in iPod.
- Video-playback is average. Screen is not the biggest and limited codec supported, which means you gonna convert the videos into compatible format (most commonly WMV).
- Noise-canceling only works with the bundled earphone.
Otherwise, it's a real nice piece of gadget to enjoy music-listening to another higher level. :)
P/S: It is OK if you can't really differentiate the model based on the pic, because the design is more or less the same. It would have been better if Sony put in some effort to make each of the series' design unique so that the consumer can easily recognise the model instead of scratching into the details (which most of them wouldn't bother much).