I bought the KX3 on a whim, if I'm honest I lose patience with QRP as I have less spare time than I used to have. I like the idea of QRP, but you have to wait for ideal band conditions and those rarely coincide with my free time.
I bought the kit version and found the build up to Elecraft's usual high standards, everything fitted together perfectly and the chassis has a quality, solid feel to it. The build took a few hours over a couple of nights and no problems were encountered.
Using the radio was slightly less rewarding, basically the radio does what it is designed to do and not what I wanted it to do. For instance:
1) The external speaker reveberates with a buzz sound when the volume is turned up to comfortable listening levels and a large signal is received. Even when external speakers are attached, the KX3 audio amplifer has distorted output on large signals. This is because the radio was designed with low current consumption in mind. Don't expect to fill your shack with booming audio as this isn't possible or desireable on a windy mountain top.
2) Want to connect a linear amplifer? Want your computer to be able to key the KX3? Well the KX3 has a crap minature 2.5mm stereo socket ACC2 to take care of that. Fiddling about with this I realised that this wasn't likely to stand the test of time. How many times would you require to connect a linear amplifier and a laptop to the KX3 on a windy mountain top?
Anyway you get my point, if you want a radio for a windy mountain top the KX3 is great. If like me you are more likely to use this radio the most in your shack, then this is the wrong radio for you.
On another thought train, there are some annoying "features":
1) The buttons are akin to poor quality telephone handset keypads. Sometimes you press and get nothing, sometimes you press and get a double press. I don't remember the same response from the K3 keypad which is similar in construction, so why is the KX3 different? Maybe the designers figure that you'll have shakey hands on that windy mountain top and they have configured the firmware button debounce logic to counter it appropriately.
2) Turning the VFO on bands above 20m emits a burrrrrrrrrrrrrp sound from the speaker (stretched out till you stop turning the VFO. It is at a very low signal level, but once you've heard it, it will annoy you senseless. Yes there are menu items you can select to lessen the effect, but trust me, the noise doesn't completely go away. Some of them also have side effects like disengaging the roofing filter. However I'm sure when you connect a decent antenna and you are on a windy mountain top you'd never notice it.
3) The manual is full of features that haven't been fully implemented yet like DVK, NR and NB. But who is likely to be examining a manual for the finer features of the KX3 at 3000ft in the middle of a snow drift.
Again, you get what you pay for, which is not necessarily what you wanted. Reading eHam reviews and the Elecraft mailing lists makes sense when you try to figure out what the user has been using it for. A high score normally means the owner also has crampons and an ice axe.