Software and drivers: 5/10
While I appreciate high quality audio, I would not call myself an audiophile mostly because I don't have the money to spend. That said, I'm quite satisfied with the Apogee Groove because the hardware is rock solid and it fits my needs perfectly.
My Sennheiser HD 58X Jubilee's sounded great out-of-the-box connected to my laptop when they arrived right after New Year's. But after breaking them in for a couple months, I wanted to discover their full potential. To my pleasant surprise, Massdrop dropped the Apogee Groove, boasting a compact DAC/Amp with plug-and-play functionality. I appreciated the form-factor more than anything else: it's small, portable, requires no external power supply, and has a built-in volume control. Perfect for my needs.
I find that it drives my 150 ohm HD 58X headphones VERY well. The Groove provides a comfortable listening level at 15%, a loud listening level at 50%, and a painfully loud listening level above 75%. In other words, there's lots of headroom and very little to no distortion. Surprisingly, the DAC/Amp performs just as well at very quiet volume levels, too. Bass and treble do not seem to vary as the volume is turned up or down. I wouldn't say the response is perfectly flat across different volumes, but at normal listening levels I have not experienced any ear fatigue. This may have more to do with the headphones I'm using (I have nothing else to go on) but compared to my laptop computer's headphone jack, the sound quality is just as good while providing much more volume.
The only real downside is the Windows 10 drivers. First of all, Apogee requires you to register the product before you can download the drivers. It's not a big pain in the ass, but it's an extra hoop to jump through which I wouldn't expect at this price. Second, the firmware update program doesn't work, it crashes with an error message. I chalk this up to inexperience on their part; Apogee makes hardware that works for Apple computers hassle-free while their Windows drivers are an afterthought. None the less, once I installed the driver, the Groove worked almost flawlessly. My only real complaint is that the audio routinely stops on cue every 60 minutes. When this happens during a YouTube video, refreshing the page fixes it. But when using a media player like foobar2000, I have to close the program and re-open it to make the audio work again. It's inconvenient, to say the least.
Still, this DAC/amp is almost perfect for me. It's solidly built, the soft rubber buttons have a satisfying click when pressed, the entire bottom surface is a grippy foam rubber pad that holds the device in place, and nothing else I've seen is as compact and portable. The device itself does get fairly warm during use, but not hot. I have only minor complaints about the design (the micro-USB port is upside down, the LED's are loosely mounted within the case, etc.) but overall I expect the Apogee Groove to last me a long time, and if they ever fix the software/driver problems, I would give it 5 stars instead of the 4 I'm giving it now.