* Prices may differ from that shown
As an intro, I might as well disappoint any audiophiles: the sound on a computer is generally compressed, lowering the quality, and in most speakers, the soundcard limits the sound further. Even speakers as good as these can not overcome the first issue. The second issue, that of the soundcard, is slightly different.
The unique selling point of the Logitech Z-Cinema speakers is that the problem with the soundcard is bypassed through USB, with the drivers (software) doing all the work. This theoretically should provide a huge improvement for lower end laptops, on top of the fact that the speakers give a very rounded sound anyway (I tested there normal sound by connecting it with a standard 3.5mm jack to an ordinary soundcard). However, it probably won't have this effect, because USB is not designed to deliver sound in realtime, so slower computers will lag, making the sound stutter.
In addition to the speakers, a remote control is included. Unfortunately, to take full advantage of this, one would require a TV tuner, which I don't have. However, there is no reason why it wouldn't work, as it hooks into Microsoft's Media Centre. The layout of the remote is straightforward, with buttons where you would expect them and a prominent volume control. My only criticisms are that there is no alternative on the speakers to control volume (so don't lose the remote!), and it doesn't work on Youtube.
Finally, Logitech have marketed the "Trusurround HD" feature which supposedly makes the speakers sound like 5 speakers around you. Personally, I hate this feature as it makes me feel disorientated, especially in games where the music seems to only come from one side. That said, it definitely works, and friends have commented that they enjoy the sound.
To conclude, if you have a computer with only support for 2.1 speakers, you'd have little problem with these speakers. They sound as good as computer audio will do (which is more than enough for anyone who isn't an audiophile), they are aesthetically pleasing, and the remote is a nice little addition. However, if you have a more powerful computer, or just want to spend a little more, then have a look around for 5.1 speakers from better known speaker manufacturers.