Logitech notes that it tried to keep the speakers' design as clean-looking as possible. For instance, there are no physical buttons for the volume controls. Instead, there's a touch panel in the top of the right speaker (you rotate your finger in a circular motion to "dial" the volume up and down -- I found it very responsive). Of course, you could also adjust the volume from the Bluetooth audio source, too.
Also, on the back of the right speaker, the ports for the auxiliary input and Micro-USB connection (for firmware upgrades) are hidden with little rubber plugs. The only problem is that if you want to access the ports, the plugs are difficult to remove -- I had to use a paperclip to pry them out. That said, it's a relatively minor annoyance, particularly since it's unclear how often you'll need to access those ports.
While the marketplace has been inundated with Bluetooth speakers over the past couple of years, the vast majority of them are "portable" Bluetooth speakers with a single enclosure design -- those are easily transportable, but not good for stereo separation. By contrast, Z600's traditional stereo (left and right) speaker design means you're getting true stereo separation.
The first thing you notice about the Z600s is that they're capable of playing very loud and will fill small to medium sized rooms with sound. Also, after listening to so many portable Bluetooth speakers where the "stereo" drivers are so close together that they basically produce mono sound, it was refreshing to get real stereo separation from a pair of speakers that could be spaced well apart.
Logitech says each speaker has three drivers. As I said, they can output a lot of sound, but the problem is they just don't output a lot of bass at higher volumes. At higher volumes, they don't do very well with complicated tracks with a lot of things going on at once (various instruments, vocals). The music ends up sounding a little squashed.
But when you lower the volume to more modest levels, the speakers sound quite decent. In other words, if you're sitting at your desk and listening at a reasonable volume (most people don't blast their music at close range), they offer good clarity and a reasonable amount of bass. So, yes, these speakers can crank the sound, but the sweet spot for quality sound is at about 40 to 50 percent volume levels. I know that may sound a little strange to some people, but many inexpensive speakers have their limitations and while they're capable of sounding good, they may only sound good in certain ranges.
As far as comparison products go,-- also a left/right stereo design -- are capable of delivering more bass at higher volumes. When first launched, those speakers cost around $250, but they have just been discontinued, so the remaining inventory is being blown out at discount prices. They don't have all the bells and whistles of the Z600s, but they do sound a bit better overall.
When they go on sale in August, the Z600 speakers will carry a list price of $149.99. That said, Logitech's speakers have often been discounted online. While the speakers don't sound as good at higher volumes and don't have a terribly swanky look or feel (no, they're not premium multimedia speakers), they're well designed and offer a couple of nice extras, including the USB transmitter for computer connections and responsive touch controls for volume adjustment. I wouldn't call them a bargain at their list price, but they are recommendable, particularly if you can get them for a little less.