I've been vacillating about making this post all day but have finally decided to write.
The H40s remind me very much of a junior IT04 but without the higher harmonic sparkle. Coherent sound, from the deep bass to the neutral but clear treble. I think that sums up the H40s very well - balanced / very mild U shape with a wide soundstage that is of average depth. The supplied ISN S8 is an excellent match for these phones.
@Dsnuts first post in this thread is a great introduction into cable rolling and I fully endorse his findings. Although the copper cable I made smoothed and warmed the sound, on further listening it was probably a little too smooth and warm for analytical listening. The Penon CS819 hybrid was interesting - the soundstage was wider with a tighter bass but the treble was essentially the same as the SPC - neutral and lacking an element of top end air / harmonics that would really make this set shine.
I cannot fault the build quality: the MMCX connectors are rock solid. The nozzles look a little short but the semi-custom resin extension into the nozzles allows for a fairly deep insertion with foam tips. They rest easy in my ears without discomfort. The little hard case is excellent and there is a generous selection of silicone and foam tips.
Compared to the TRI I3 these sound cooler and more analytical with a drier, crisper sound. The soundstage lacks a little height and depth compared to the I3. This is all relative, mind - the H40 by itself is a great IEM and good value for money. I'm very glad I tried them. They are a mature and confidently designed product that is well worth auditioning and had I not the I3s in my possession, I probably would have been very happy with these. What can I say - the ear wants what it wants!
In the end, it will come down to how you like your music - both sets are mildly U shaped but the H40 is more neutral, the I3 sweeter and more musical.
After all that, I will be putting my pair of practically new H40s up for sale. I will put a sale thread up after the weekend but if anyone is interested please PM me with a sensible offer. UK preferred.