This is the worst MP3 player I've owned, and that includes the Microboss player that clipped tracks and the Tesco Technika one with a constant background buzz. It's also known as a 'Squircle' and several companies rebrand them or sell generic versions, including Proporta, Uxcell* and Sumvision, but Sitecom win the prize for managing to fuck up implementation even of a design as simple as the MP310.
The biggest problem is that the player resets to the beginning of the file list every time it's switched on. Since other people reviewing these type of players state categorically that theirs don't do this, I suspect Sitecom got a very early version of the firmware.
The player has two different-coloured LEDs to indicate functions, built into the buttons. Sitecom have helpfully put opaque rubber over these (without the transparent inlay other manufacturers use) which means they're invisible except in near-darkness.
The buttons themselves are unbelievably bad. You can hear them click, but they tend not to do anything without further pressure and wiggling. Sometimes when the player springs to life it only manages to play half a second before switching itself off.
Oh, and the player appears to form a circuit and drain the battery even when off.
The only plus point is that the person I bought this off refunded the full cost including postage. In theory it's a nice idea — just put in a card and a battery and it works. Indeed, the sound quality isn't too bad when the damn thing functions. But as built it's an utter waste of space, and does nothing to justify its shiny and more-than-usually-professional packaging. Steer clear.
Some other reviews:
*Other sellers over in China and Taiwan also seem to use the same circuit board in a more square shell, with five circular buttons arranged like the dots on dice.