Anyone hoping the Walkman NWZ-S544 would score as well as the NWZ-E443 will be disappointed. While in isolation it's still a decent media player, it's something of a step if not necessarily backwards, then definitely sideways from its S Series predecessor. And different doesn't automatically mean better.
The changes are immediately evident. The S544 is noticeably bigger than the NWZ-S639F. The reason for this increase in size is that, keeping with the current inclination towards adding slightly gimmicky features (hello, iPod nano), Sony's refreshed S Series Walkman comes complete with built-in speakers which add a fair amount of size (though not weight it should be said) to the player.
Admittedly there are benefits to having built-in speakers. Laying in bed with Charlie Brooker's Gameswipe transferred to the S544, for example, it's possible to keep the volume low enough that there isn't any distortion. Although with the volume down it might be hard to hear the programme over the raucous laughter it's likely to induce. More practically, you can use the S544 as an alarm without needing to sleep wearing 'phones (which is just a little impractical) or leave a set of speakers plugged in and turned on.
In the outside world, however, using the player's speakers is nigh unforgivable. I can't say I've ever been inclined to sit in a bus or train and blare out my music for everyone else to 'enjoy', which is probably very uncharitable of me because I have impeccable taste. Annoyingly, however, not everyone is as restrained as I and the quality of the 544's speakers at volumes loud enough to hear anything in anything but a totally quiet environment mean that what you do get to hear is an incoherent mess of noise.
In fairness to Sony, no speakers this small are going to sound amazing and it's hardly any engineer's fault if today's youths decide to misuse their products. Besides, the E Series is there if you prefer a smaller player.