Well I had a week with the tour preamp before sending it off to rklein. I am currently running everything through a Marantz SR-6005 AVR which serves as a preamp. I am currently changing my whole system around. I hooked up the preamp out to my Pass ACA DIY amps. For inputs I used my Technics SR-1200 turntable through a Vista Phono1 preamp, a Schiit Modi DAC fed via USB from a Raspberry Pi running Volumio, and the Marantz AVR preamp outputs to check out Home Theater Operation. My speakers are Boston Acoustics HD-9s.
I listened to a varied selection of my music which is mainly rock and folk. For the albums I listened to just check out the What are you listening to? thread in the Music Circle.
I don't listen to my turntable all that often since it normally sounds like I am hearing the sound underwater when playing it through the Marantz. So I was planning some upgrades in that area (have a new arm and wiring on order). Playing it through the Tortuga preamp was a definite improvement. The sound was much clearer and more detailed.
Most of the time I listened to ALAC files streamed to the Raspberry Pi from iTunes on a PC. The sound was very clear and detailed, but without the air of sibilance that I experienced with the iTube2 I had in my system for awhile. Definitely made music listening enjoyable.
I tried running through the preamp with a signal from the Marantz preouts as a HT bypass application and set the volume to 99. It worked and sounded great.
I did have a few issues with the unit. If you have an appleTV like I do, you either have to change remote settings or unplug it like I did. The remote worked OK after that. It took me a little time and checking out the Tortuga website to figure out how to operate the controls. Once I got the hang of it, it seemed to work fine. I didn't delve to deeply. I just changed the volume and the switched inputs.
All in all I liked the preamp board and I am looking at picking one up as soon as Morten gets the Uart serial control all figured out and released. I intend to add it to DAC/DSP/streamer DIY build that I am currently working on. I am going to use an Arduino to control the preamp and DAC with an LCD screen and a pair of eductors.
Here is a picture of it in my system:

Morten, thanks for the tour and the chance to hear this in my system.