I got these in the previous drop, and I'm extremely impressed with them. I initially had an issue with the left side cutting in and out, but after reseating the cable connection everything was fine. These are my first set of IEMs with multiple drivers and balanced armature configuration, so I can't offer any meaningful comparisons with other IEMs in this category. Until I bought these, my best IEMs were an old set of Sennheiser IE7s. The Senn is really a nice piece of work, getting very balanced sound with everything in place, albeit without a lot of slam or shimmering high end. In any case, the Primo 8 is another beast entirely! My constant impression is that these are an exciting listen. Bass is fast and quite deep, although not quantitatively where a real bass head would want it to be--it's slightly lean. They have an excellent and musical midrange, and extended and dynamic high end. They're engaging with just about any kind of music, and they reveal details without being harsh or zingy.
I've been listening to the the soundtrack from Gladiator (damn it's good!), and the Primo 8 exhibits excellent separation of instruments in even the most complex passages. To see how it dealt with something more driving I've been using Peter Gabriel's Security, in particular "The Rhythm of the Heat," ""I Have the Touch," "Shock the Monkey," and "Kiss of Life." Between those songs, you get a great selection of tribal drumming, drum machines, Jerry Marotta working the kit so hard that the drums were probably still vibrating half an hour after they turned off the mics, fine bass and Stick playing by Tony Levin, and Gabriel's remarkable and complex voice. The Primo 8 served all of that goodness up with aplomb, making me want to listen more and louder. Acoustic and vocal centric music like Jimmy Webb's recent albums and Vince Gill also sounded great, as did Diana Krall. These IEMs are just fun to listen to.
Fyi, they work quite nicely when plugged directly into my iPhone 6 Plus, hang together well with the Shanling M2(despite it's slightly high output impedance), but they really shine with my phone feeding my ifi iDSD nano. I don't have anything further in terms of amps/DACs to try them with. I guess I should also mention that all the source files were ripped from my CD collection and are in either alac or aiff formats.
Anyway, while I don't have the familiarity with competitive products either with IEMs or amps, my ears have been tuned on a pretty outstanding speaker system, so I'm not without audiophile experience. I think the Nu Force Primo 8 is a fantastic set of IEMs for the drop price.