I have one. I love it. I might even buy another. I've got a few samples using one if you're interested. Below is my review I posted at
www.Harmony-Central.com
Ease of Use: 10
The Tech21 Acoustic DI is basically a DI with some EQ controls and a tube "blend" control. Very easy to use. The manual is very good and gives some good starting points for dialing in a sound. Powered by phantom power is an awesome feature! I also love the i/o options. I don't use the loop as an effects loop, but I do have it going to a tuner and sometimes an amp.
Sound Quality: 8
The sound quality of this unit is top notch, depending on what you're doing. For live, the box is mana from heaven. I hate piezo's, but mic'ing isn't always the best option. I'm able to get a good live sound and kill feedback with the mid/notch control. For my steel string, it takes a bit of tweeking depending on the mood my axe is in. For my nylon string, it doesn't matter what I do live, I can get a good sound... even with the box in passive mode. For recording, you'd be hard pressed to find the sound believable as a tube mic'd guitar. My nylon sound is very usable recorded with it. I've used it with my electric and a Sansamp Original and got some very good recorded tones. I even tried it as an insert on some vocal tracks and got some good results! Live I'll give an 8, recorded I'll give a 7
Reliability: 10
Typical Tech21/Sansamp. Built like a tank. I've had mine for 3 years and no probs whatsoever. Both of my acoustics have xlr outs, so technically I don't even need a DI, so yeah... I'd gig without a backup.
Customer Support: 10
Awesome!!! I've only dealt with them regarding
my Sansamp Original pedal and they were very supportive, polite, and prompt.
Overall Rating: 8
I play primarily fingerstyle... open/alternate tunings, blah blah blah... I do gig and do record.
My Sansamp Acoustic DI definitely gets used and has been a very useful tool in my box. It is pricey, but I know I've gotten my money's worth out of it. If stolen or lost, I'd replace it.