I couldn't help myself and ordered a Pico Slim earlier this week. #0494 arrived today and my ES5's are back at Westone for a refit. If I opened my mouth, even half way, i could break the seal. It was evident when mowing the lawn. For some reason, the noise generated by the John Deere was the easiest noise to hear the change when the seal broke. My Audiologist made two more molds. One mold with my mouth open and one with my mouth closed. She instructed Westone to create the new mold using the largest part of both sets of her molds so that hopefully the seal can't be broken no matter what facial expressions I make.
So, while I wait for the ES5's, I am stuck with my bass-heavy V-Moda Vibe Duo (or something like that). But I can say that the Pico Slim paired with my iPod Nano sounds great.....even with 320k MP3's. The difference between unamped and amped from said source is definitely noticable. Everything is tighter, crisper, clearer and extends further at both ends. I can't say the volume is actually louder, but maxed out the music is clearer through the Slim. I don't know if it's worth $400, but the form factor is quite nice paired with the nano.
I am having a problem with the Slim and iPhone 4. When I connect the Pico Slim to the iPhone 4 and use FLAC player, the Pico Slim acts weird. If I turn up or down the volume quickly, I hear the left ear adjust a split second sooner than the right ear. Now, that's with the volume going up and down, the change happens in the left ear first. I also hear static when rotating the knob.
Now, the Nano-->SOLO-->Pico Slim-->headphones sounds really fantastic. (hopefully even better with the ES5) I just wish I could carry it in a stack like that. But it's summer and there is no way that's getting shoved into a pocket. For now, the work rig will be the SOLO/RX MarkII/ES5 and the rig in my pocket will be the Nano/Slim/ES5.