After a 2-month shipping delay (thank you, Swedish post office) I got my QCX transceiver serial #3461 in April 2018, and built it over a few evenings. I can highly recommend this transceiver. It was the first kit I ever built, and everything went perfectly thanks to good design and a thorough manual by Hans Summers G0UPL. The only problem was that power output initially was much lower than expected, an issue traced by several other builders to the 560 pF capacitors used in some 30m versions of the kit. After replacing those I now measure 3W out with a 13V supply, increasing to 4W at 15V. The transmitter is simple and functional, but the best thing about the QCX is the receiver: a single-signal receiver with a good 200 Hz CW filter. It is a joy to use on the air.
If you have the GPS module or some other frequency reference, use that. Otherwise, I found that the Reverse Beacon Network (RBN) is useful for calibration purposes. Just call CQ, make sure that you are heard by a few stations, and note the difference between the frequency reported by your QCX and the consensus of the RBN spotters. Then you change the value of menu option 8.5 (Ref frq). In my case, I ended up with a value of 27,005,300 Hz. There is usually some variance in the reported frequencies, but you should be able to get within 100 Hz or so. That is much better than the kHz-sized uncertainty you get with the default settings.
Inspired by Lou VK5EEE (see the QCX builders gallery), I used the cardboard box the kit arrived in as a chassi. Works just fine, both for portable and home use. The LCD window is made by back-to-back transparent tape, and I added a phono jack for the straight key I use. Not particularly weatherproof, but good enough for portable operations (see below!) or in the shack.
These are rough estimates of the power output, measured using the QRP labs dummy load I got together with the QCX. Roughly in line with the 30m build in the manual.