I've had the d-JAYS for a number of months now, and there's just very little bass. Maybe I should be looking at getting a pair of Turbines or JVC-Victor FX500s to replace my Sony EX-85s (which produce great bass but very low detail in the highs) instead. I wasn't expecting these to be brilliant at producing really low-end bass, but I was still expecting these to be a bit better than they are.
The d-JAYS are extremely comfortable. They isolate sound very well if you're walking around the city streets (not really recommended for safety reasons, but it's something I do often), sitting in a café near people who are chattering away. Also, the way they sit in your ear means you can sleep with them on. You don't feel them. It's not a huge deal for me unless I fly, and I do fly internationally quite often. I can wear them for hours without feeling discomfort.
Also, my source is generally a Nokia 5800 XM (Xpress Music), which comes with a remote control for play, pause, skip forward and backwards, etc. The length of the d-JAYS cables are absolutely perfect for me, and I'm 5'10" (177 cm).
Anyway, I can't say I'm disappointed with these unless I listen to hip hop or dance. They're great for indie rock, and some dance (dance-rock) tracks, but I like to have some bass with those tracks. These don't really provide much punch. The bass is definitely present, but the d-JAYS aren't recommended by me for those who are going to listen predominantly to dance or hip-hop.
I bought two pairs of d-Jays for myself and my wife 2 years ago and we've both had problems with the build quality ever since. The wires are so small and attached weakly so that I've had to re-solder both pairs of headphones as well as the extension cords.
My solders hold fine, but now one of my wife's buds has stopped working and I'm tired of fixing them.
Jays didn't send us a case with these and they are really delicate, I just wanted to warn potential buyers of our problems.
Now I'm in the market for more robust in-ear phones, and rather disappointed that Jay's ruins such great sounding phones with poor craftsmanship.
My roommate recently purchased these and from demoing them I have to say I'm pretty impressed. The sound range was way bigger than I was expecting from them, and it handled heavily-distorted music with surprising clarity. The bass sounded a little too rounded for my tastes, but that might have just been how my roommate decided to EQ them. Either way, they seemed to me like a great purchase for the money.
Can't really give any input on durability/build quality since they're still so fresh. I'll check it out after some time passes since he goes pretty rough on his buds and post here.
I actually find the d-Jays a more impressive product than the q-Jays, at least for the price. Bass quantity differences between the two isn't huge, but is noticeable. But, the d-Jays perhaps are smoother, or... not sure what, but I prefer them.