Pros: Lightweight, great performance, ease of use, great sound with basic controls.
Cons: Bluetooth only, no provision for hardwired connections.
Let's start off with what the Sennheiser MM 100 headset isn't and what it is. It clearly is not a replacement for over the ear tuned sound chambers. This is a lightweight, innovative set of on-ear headphones which is a step up in sound quality from even the best wired earbuds with the convenience of wireless operation, built in microphone for making phone calls and basic controls. These are closer to smartphone earbuds than to studio headphones but they still deliver, especially for the price.
The design incorporates a semi-flexible hoop which provides mild tension to keep them in place in a hooks-over-the-ear design which is surprisingly comfortable and secure. Even running or doing yard work will not shake them loose. A tennis match probably would and sticking your head out the window of a car moving at speed will probably have them flying off. That said, they're easy to put on and take off and they're very comfortable.
Controls are all on the right pad. The on/off switch is in the center of the pad and volume up and down and skip forward and back are arranged bottom and top (respectively) on the edge. The micro-USB charging port is located on the left pad and is covered by a captive plug which is such a nice fit that it simply disappears.
Pairing was void of the usual Bluetooth drama. Press the skip button after turning them on and then go to the device you wish to pair with them. This implementation of Bluetooth does ask for the "0000" passcode but after that, just turn them on. Then they and the device find each other in about one second. No hunting or "can't connect" messages.
Sound quality is excellent. Highs are crisp. Stereo separation is accurate. Low notes are reproduced well but not with the brain-thumping one would expect from an over-the-ear heavy set of headphones. Volume was surprisingly good. It was all I could stand before I reached the maximum volume setting and it is very, very nice to have up and down volume buttons on the headset so I don't have to take out my phone and make an adjustment. I would classify sound reproduction to be as good if not better than the best premium earbuds available.
Skipping forward and backward in a playlist is easy with the skip buttons on the right pad. One cannot move from playlist to playlist, however. Again, this mimics the skip function on most earbuds, not a full set of navigational controls.
Telephony actually works with this Bluetooth device without lags or cutouts. I was very impressed by this. Other devices have always had me saying, "Hang on" as I disconnected the Bluetooth and went back to regular phone use. Not with the MM 100 set. Calls politely interrupted music and when the call was over, the music resumed. I was told by those on the other end that I sounded "just fine" to them. The on-ear design also gives me enough sound feedback of my own voice so I don't end up screaming without realizing it until all eyes are on me. This is an area where these work much better than any earbuds which isolate me from my own voice to the point where I have to remind myself to speak normally. This really was a very normal conversation and hearing the caller through both ears really beats one of those one-ear devices all to heck.
The MM 100 set has impressed me with excellent, if not studio sound, good volume, ease of use, comfortable fit but also with battery life. I have been getting a full day of use on a charge without any problems. I would estimate probably 8-9 hours of use with no sign of the battery flagging. Charging is a relatively quick three hour process using the included mini-charger and cable. The cable can be plugged into any USB charger or the USB port of any computer. The charger does not need to be carried around. That's good because the only drawback is that the outlet prongs of the charger do not retract. They stick out so putting this in a pocket would be a bit difficult. Throwing it in a bag would probably not present any undue problems though. When charging, the headset is disabled for safety. The manufacturer states that it is unwise to charge any battery in any device next to your body. This is very good advice and it is why all functions are turned off when the headset is charging.
The manual is written in a dozen languages and makes it seem more imposing than it really is. A quick start pictogram flyer is included which had me up and running without reading the manual in any of its languages.
There is no input port for other devices, so this headset is Bluetooth only. One cannot plug it into a CD player or other non-Bluetooth device.
All aspects considered, this headset is well worth the $150 price. They are rather durable with some care, easy to use, comfortable to wear and provide sound great. They met or exceeded my expectations across the board and have allowed me to enjoy my Norwegian polka music while writing this review without sending others near me to various state facilities for treatment. :)