To my ears, there are very little microphonics, NO occlusion/bone conduction (aka, "foot-step syndrome"), and I effortlessly achieved an instantaneous, seamless fit with the default tips attached. I haven't even experimented with the other two sizes. I just don't want to take them out of my ears, I don't want to spoil this perfect experience.
Beyond comfort, there is so, so much more I can say. The SQ on these things have given me chills, and made my heart go "thump" more than a few times. When I have the time and opportunity, not mention some more burn-in hours clocked, I am determined to write these an extensive review. The HJE900 simply deserve it. I feel like I owe Panasonic my written gratitude.
Thank you guys for bearing with my nit-picky questions, and thank you to all who posted in this thread, having finally convinced me they're worth the purchase--which they certainly are