I am very happy with my C6802 almost 11 months after getting it (bought it early August last year). It is still unsurpassed and despite about three weeks before root was possible (vRoot unfortunately), the arrival of GPe got things going.
It is the best phablet made to this date; I don't consider any other device close beside the Oppo Find 7. The only thing I am worried about is the lack of any successor rumor or even information about upcoming devices in the same category. The only competitors I know about right now is the Oppo N1 and Huawei Ascend Mate 2, both with weaker hardware.
My requirements for a new device is Snapdragon 810/815, 4 GB RAM, 64 GB internal storage, 6.5-7 inch screen, keyboard cover as an option, camera not important (have the QX10 for that), microSDXC slot and... either Google vanilla/Android Silver or CM-based. Sony implementation is OK.
I guess next year will bring those things to the table but it would be great with some decent phablets this fall since it would indicate that the segment is alive and well. Right now, the Ultra is in a class of its own and any other device means compromising on the core: a solution that is a true tablet replacement with great software.
Edit: The GPe ROM paired with Xposed Framework and optimized Dalvik libraries (compensating for the ART/Xposed issue) make the Ultra a completely superior phablet. I have tried the Note 3 (which is hyped as being such a great device) several times and it is far, far behind the Ultra in every aspect besides the camera. The best features of it such as multiwindow is available on the Ultra through Xposed and it works great.
[Xperia Z Ultra C6802][ROM: GPe 4.4.4][Launcher: Nova][240 DPI]
[Xperia Z C6602][ROM: PAC 4.3][Launcher: Nova][240 DPI]