I wasn't expecting much from an MP3 player this cheap, so I was pleasantly surprised. Let me begin with the advantages of this device and finish with the drawbacks.
The fact that modern technology lets us play 320KBPS MP3 on a device this inexpensive amazes me. It's no iPod--you won't have a fancy screen, a "current track" readout or even a random shuffle feature--but at this sort of price you don't expect those features. In a fantastic move by Sumvision these players have no built-in memory but instead take SD cards, which these days are amazingly cheap for their capacity (at the time of writing, a 1GB card for £[...]). Unlike a lot of low-price players, the capacity of this device can be expanded further and further as SD cards become cheaper and cheaper.
Playback is solid, and your batteries run out at work you'll find that the device can be powered by USB too. No software is required - the device doubles as an SD card reader for your PC, so Windows 2000, XP and Vista will automatically detect when you connect it to USB and you just copy files to and from it as if it was a disk or USB pendrive.
Drawbacks: It feels quite cheap, made of that cheap plastic that you can smell. The battery socket cover feels quite fragile, and since it connects to USB anyway I would have preferred a USB-charged internal battery (but then, I suppose you get what you pay for). Finally, it gives a "low battery" indicator even if I use new Duracell alkaline batteries - perhaps it demands high-power batteries. I found that when I ran it off normal batteries, the device had trouble playing VBR-encoded music. This isn't a problem if you're technically adept enough to reencode your stuff to CBR or can find batteries that this thing likes; otherwise you might want to spend a little more than on this device.