I have yet to find an actual neutral pair of IEM's. I'd like to try the UE Capital Records ones, which are touted at neutral but they are just too much dough for me. I can say this, the studio monitors I'm used to mixing on, Genelec 1032's plus a Genelec sub in 7.1 I find relatively flat or neutral. My small speakers are Yamaha NS-10's which are NO WHERE NEAR neutral. But I've mixed so many records, movies and commercials on them that I've gottern used to them. And that's the main point. It's what you get used to, and know and trust, which brings me to the UE TF10's. For my ears, the TF10's hold up really well to Genelec 1032's, and is what I reference my mixes on when I drop down to ears. Yeah sure they've got a bump in the bottom, but I'm aware of that when I'm mixing and take that into consideration. I think the main thing is that you ARE listening to your mixes on ears at some point as it really challenges your reverb and delay returns. It's amazing to me how many mix engineers (and some really big names ones) DON'T even reference on ears, when clearly 90% of their mixes are going to be heard on those POS white Apple headphones. Which is another philosophy, just use those Apple ones for mixing, but I can't get those things in my ears.
Now, for audiophiles who just want to hear high quality IEM's. Well, since there really is no neutral that I know of, it's kind of a season to taste and what you get used to. That's why each company (UE for example) makes so many different models. Over all, I much prefer the TF10's to the UE 900's but both are high quality IEM's. Ultimately what I've decided to do is keep my UE 900's for working out, mowing the lawn etc, and have my TF10's re molded with customs by 1964 Ears. Those will become my mix phones and 1964 Ears says it retains 95% of the original signature. I'll still keep my UE7's for stage work, even though they are bass light, they really seem to work well onstage as you get a fair amount of bass from wedges, bass amp, and FOH from behind. It all seems to even out.
My 2 cents on a long winded explanation.