Just got my UE900s today. Listening right now to some high res FLACs. If it's true that these will improve with run-in, then I have something stellar to look forward to! They already sound really nice!
Pretty comfortable too. I fiddled around with different size tips, I ended up using the middle size.
It's not exactly run-in, more of the physical blockage of the mini-bore of the IEM with earwax and stuff. For tips I recommend using the T-500 Complys (same ones for TF10).
Edited by Peculier - 12/18/12 at 5:48pm