As with the Flip II, the key to the X300 is that it doesn't distort, even at higher volumes. The reason for that is Logitech's engineers have done a good job with the digital processing, making sure that the speaker doesn't get overloaded. Sometimes you can hear that processing kick in and restrain the speaker, which isn't good, but it's better than having the speaker distort badly. At least I think so.
In all, I liked the X300 and have no problem recommending it. It doesn't come with any sort of carrying case or have a pause/play button on the unit itself (except for volume, you have to control playback from your smartphone or tablet). Also, battery life is only so-so at around 5 hours.
But apart from those small gripes, I didn't really have anything to complain about. It's got a sturdy, attractive design -- it weighs 0.80-pound or 0.36kg -- that seems suitable for both indoor and outdoor use and offers decent sound for its size. The speakerphone also works pretty well, so long as you don't stray too far from the microphone, which is on the top of the speaker.
I'd take the better-styled X300 over most of the generic $50 Jambox knock-offs out there, as well as a lot of the more established mini speakers, including the UE Mini Boom (Logitech owns UE), which tend to retail for closer to $100.
In short, in a sea of tiny Bluetooth speakers, the X300 is a good catch -- a keeper, if you will.