Just got these today. Some quick initial impressions...
Presentation
Fantastic, especially coming from a company like Mee - they didn't have the best reputation on this front before. They're packaged well, and the wires aren't wrapped in an annoying fashion (RHA does this terribly). No complaints.
Build
Outstanding. The cables seem solid (and quite heavy!), and the IEMs are super-solid. The plug is L-shaped, which is awesome for pockets. I'm a bit worried about the lack of strain reliefs - RHA's spring coil, or AT's plastic thing set my mind at ease a bit more. I'm using the silver cables. A quick note about RHA cables - they seem sturdy, but I've had multiple cables break on me. Either the insulation would break, or the memory wire broke, or some crazy thing would happen. A replaceable cable would work wonders for them, and I'm glad the P1s went with this.
Ergonomics
The shape is lower profile than the RHA T20s and the ATH-IM70s (my previous two IEMs). They weigh more than the IM70s, but are lighter than the T20s. This is a good thing - the IM70s seemed delicate, and the T20s were annoyingly heavy and ended up hurting after a while. The cable isn't the most flexible thing in the world, though. It doesn't seem to get tangled as easily as others. I semi-wish they had a memory wire because the weight doesn't quite seem to distribute correctly, although a memory wire does seem to make things more delicate.
Sound
Power requirements
An iPhone or Macbook Pro will do fine. The iPhone needs to be at around 50-60%, and the Macbook needs around 4-5 notches. I didn't detect any weird factors, so I don't think they're source-dependent. I also tried them out of a Vali 2 amp, and the volume knob is at 9:30, low gain. Any higher is too high for me. No hissing or scratching can be heard. The low sensitivity and high-ish impedance (especially for IEMs) is a benefit here. I'm assuming, therefore, that any smartphone should work well, provided smartphone maker didn't half-ass something.
Bass
Bass-light, but as others have said, they do still have a good amount. I find that the bass on the T20 (reference filters) is too strong (and yes, I've heard the T10s as well - the bass on the T10s was unlistenable). Compared to the IM70s, which had surprisingly strong, but controlled bass, the P1s are even weaker. Again, this isn't to say that there is no bass - it's there when you need it, but only just. I'm not detecting any bloat or bleed into the midrange, and this is a good thing. Like the IM70s, the bass on the P1s is well defined. A bass guitar doesn't sound anything like a kick drum, for example.
Mid/Treble
I generally don't separate the mids and treble - they're a package deal in my mind. Voices and sound effects sound realistic (clapping sounds like clapping, dudes sound like dudes, gals sound like gals). Cymbals sound like cymbals, and not a random splash of treble. I think this is where people are getting impressions of warmth - The mids have a good amount of weight, and the treble isn't super peaky. The T20s had a slightly annoying peak to them, and the IM70s were slightly rolled off. The P1s don't seem to suffer from either problem.
Soundstage
Quite good. I can place instruments and voices easily, and there's no congestion going on. The T20s and IM70s had pretty good soundstage as well, though, so the P1s aren't really different in that regard.
Overall
I like these! They're quite versatile, and have no outstanding issues. Mee seems to have thought of everything, and while the bass could use a bit of a boost, that can be easily remedied (I EQ'd the 32hz band a 2.5 db, and raised the high mids a bit).
