I've had my UE900s for a couple of months now and I've been very happy - with the SQ anyway. I find them to be very resolving with a wide soundstage and a great pairing with my DX50 for on the go use. So far, I've had no problems with reliability, but it's early days yet. I bought these off Taobao and got them pretty cheaply, so I reckon I'm getting hi-fi sound for a lo-fi price. In fact, the DX50 / UE900 is pretty incredible bang for your buck.
I am disappointed in the build quality though. They're very plasticky and I was hoping for something more refined. The box comes with a remarkable amount of stuff in it - twin cables, an airplane adapter, a hard case and soft pouch etc. I would rather they had saved on the extras and improved the overall build quality tbh. They're also not the last word in comfort, but the fit is acceptable I guess.
Still, they sound pretty stellar, and that's what counts, right? If you can get these for the right price (I paid 1400 RMB, about 230 USD), then they're quite the deal..