I do not own this unit – I had this unit from @fnkcow
 
With Impedance of 320ohm this earbuds need a good amp to show its worth. I use my phone during my first listen to the zen and it sounds cold, sterile. Using the zen with my oppo HA2 or cayin N6 (which has monstrous power) reveals their real sound: good bass, forward sounding mids, smooth highs. With proper amplification the zen gives a wide soundstage and imaging, good instruments separation and layering. The shells looks to be a generic earbuds design, which doesn’t seem to be a good choice for a flagship product. The earbuds are wired with a decent OFC cable that feels nice to touch and have slight microphonics when touched.

Disclaimer

I do not own this unit – I had this unit for a few days as part of an Australasian tour. Thanks to [color=#22229C]@Brooko[/color] for providing his own unit for this tour.
 

Build

Honestly I didn’t expect a $100 device to have this build quality. Solid aluminum with machined buttons, although the plastic scroll wheel feels cheap and detracts the overall value.
8.5/10
 

UI

The UI is an okay to me, while some buttons seems redundant at times. For instance pressing the lower left/right buttons in folder browsing simply moves the cursor to one item over/under, I can see an improvement for future firmware to change this into page scrolling instead.
I personally think the unit need some rework in the line/headphone out department. The option to switch between the two is hidden inside system settings (took me a good 10 minutes before I found it) and requires you to manually pause currently playing song instead of doing it automatically when you switch options.
7/10
 

Accessories

FiiO provides generous amount of accessories included with the package – silicon case, USB cable, 3.5mm interconnect and few stick-on stickers for personalisation. I won’t be using the case and stick on as I like the aluminum feels but YMMV.
10/10
 

Sound

The X1 sounds warm, has more clarity than my iPhone 4S and less detail than DX50+C5D stack. It’s good enough to be paired with IEMs but I didn’t test the X1 with my headphones, barely tested the line out so I won’t comment on that.
8/10

Conclusion

The X1 might not be for everyone but personally I think it’s a good option for introductory DAP for its price. UI needs to be smoothed out a bit otherwise it’s perfect.
8.5/10