The design is very straightforward, with Bluetooth and volume controls spread across a small strip of plastic on the front of the device, and an on/off switch, auxiliary-in port, and the power port rounding out the rear. On the bottom of the speaker, you'll find four rubber feet to prevent the D100 from slipping across a tabletop as well as a battery cover that slides off to reveal a compartment for the four AA alkaline batteries you need to power the device on the go. Unlike the Z515, the D100 doesn't come with a built-in rechargeable battery (which accounts for the lower price tag), but Creative rates the battery at up to 25 hours of music play.
The D100 offers two easy ways to get the party started using either a Bluetooth connection from any compatible A2DP device or through the hard-wired 3.5mm connection on the back. We tested the Bluetooth setup with an HTC Evo and an Apple iPhone, and establishing a connection was as easy as holding down the power button for a few seconds to engage "discovery mode," and then just selecting the speaker on the corresponding music player. The entire process took us less than a minute on both phones from start to finish, and we couldn't ask for an easier way to connect.
The Logitech Z515 may have an advantage over the D100 in that Logitech provides a wireless 2.4GHz USB transmitter in addition to the aforementioned connection options so you can still get wireless music from your laptop without sucking up precious battery life on your phone.
On the other hand, we prefer the D100's range of sound over the Z515's across all of the test music we played through it; bass-heavy tracks are well-accommodated, and highs come out crisp without sounding tinny, an impressive feat especially for a Bluetooth speaker. The speaker can actually get quite loud at maximum levels as well, although don't expect the volume to blast high enough to get a large house party started. Bluetooth speakers like the D100 or even the Z515 are better suited for small get-togethers, not ragers.