Depends on the source material (and the MP3 encoding)
Being a recording musician, there are certain circumstances in which I can definitely hear the sonic "artifacts" in an MP3 (especially at around 128Mbps).
It's most obvious to me with instruments like acoustic guitar, especially if the instrument is prominent (and if it's well-recorded, the effect is even more pronounced). You get a kind of "sparkly" distortion which is hard to describe, but I find listening to it irritating at best, and unpleasant at worst. As I like a lot of acoustic guitar recordings, you can see why I might find this a problem.
Admittedly, using a higher bitrate helps (e.g. 320Kbps), but by that stage I see little point in MP3 when FLAC files aren't much larger. I now rip CDs to FLAC, unless there's a good reason for retaining MP3 (usually for portable players lacking FLAC support).
Oh, and the review: for this price, I'd be looking at something like a Sonos system, not an iPod speaker-dock (however fashionable)...