I got this primarily for bass, but I've tried it with guitar as well, and I can say that this is one great DI box. I got it because in many comparisons on YouTube, it either stood alongside or actually out-performed some other high dollar DI boxes like A-Designs REDDI and the Avalon U5. After that, I thought because of this and the fact that it says Neve on the box that it would be infinitely more expensive than the others, but was surprised to find that it was only $269. "Shut up and take money" was my response.
After using it, I can say that it is a great DI box. The signal that comes from it is clean and dynamic. A lot of other DI boxes cheaper than this one tend to be flat and err on the side of lifelessness and mud. But this one works great and the design is very simple and easy-to-use.
I've tried it on my bass, and it sounds excellent. My bass sounds crisp, clean, defined and full, with no loss of low end (as well as high end and clarity) that is typical of cheaper DI boxes.
I've also used it on both my guitars (one with active pickups, and one with passive pickups) with high-gain amp sims that usually don't sound that great, and it sounds just as excellent. The amp sims (LePou, BIAS, Nick Crow) have never sounded better than with this DI box, and without the sims, the DIs just sound like a really good clean channel on an amp. Pretty cool.
If there was one feature that sets this DI box apart from the others, it's that you can use this DI box to record the direct speaker output of an amplifier (as long as you have a speaker load in the "thru" end and have the "speaker" option selected on the box) alongside your regular miced-up cabinet. So you can record your regular guitar/bass amp mic'ed up, but if you ever feel your cabinet doesn't quite cut it, you can use the signal recorded through the RNDI and use a cab impulse loader like Torpedo Wall of Sound or LeCab to use the sound of a simulated cabinet.
Best of all, it's phantom-powered, so no need for finding a spare 3-prong plug like you would with the REDDI, U5 or BAE DMP.
Overall, I love this device. It gets the job done, it's easy to use, it sounds great, and I have no complaints with it so far.