Pretty damn sweet. It doesn't offer anywhere near the customization that CyanogenMod offered (running OxygenOS...) but it is still not a shabby device at all. I miss stuff like AudioFX (huge music nerd lol) and the theme engine (customization freak!) and there are bugs that are sort of annoying (SD card not being shown in settings, USSD code sometimes failing to run, etc) but, overall, the experience hasn't let me down in day-to-day life.
It might not exactly seem like I'm having a pleasant time since all the things I've mentioned till now were negatives, haha. But, well, this device suits me more than One does. Firstly, this is a smaller device - fits my hand easily and is much more convenient. Secondly, that screen. It is friggin gorgeous. The AMOLED screen really does make media consumption a treat! And, well, apart from that, the day-to-day usage is just as fast as it was on my OPO so that's great, too. :D And I can't forget about the build quality of the device now, can I? It is beautiful to look at and even better to hold. One gripe is, obviously, since the back is made of glass, it catches fingerprint marks really fast - that's a minor annoyance to an otherwise brilliantly designed piece of technology. :D