After having a few days with my Darter UltraThin, I have a few comments.
Overall, this is a very nice laptop for the price. The feature list is very impressive. I have been waiting for 1080p, 802.11AC, and Haswell all in one package for quite a while now. I would have preferred a 13 inch option as that suits my needs a little better, however I'm happy with the 14 inch display.
After opening the box, the first thing that struck me was the weight of this thing. I imagine that it's related to the touch screen, which is a feature that I didn't necessarily need, but it's pretty darn heavy. Otherwise, I have found the construction to be quite nice and have had no problems with the keyboard at all. This is my first System76 computer, so I am unfamiliar with the previous issues some may have experienced. The display is very nice, bright, and the touchscreen is responsive (when is multi-touch coming?). After installing NFS and exFAT (why oh why is this not included with Ubuntu?) I started to experiment with some video playback. Overall it's quite smooth and VLC does a good job with my bluray rips. I initially had some tearing issues but found a fix (forgot where) online. I tried updating the video drivers with the intel GUI app, but they haven't supported 13.10 yet. On to my first real complaint... the sound coming from the speakers on this thing is quite tinny and minuscule. I suppose you will always have to compromise something in a computer with this form factor. Next issue, battery life. I have waited a few days to comment on this. I was hoping that after a few cycles on the battery I would get better performance out of this thing. That was the whole reason for waiting for Haswell! However, even on dim brightness settings, I'm only getting about 3.5 hours with normal internet usage. Very disappointing! I don't really think this is System76's fault, however. It's more likely an Ubuntu power usage issue. I'm not even sure if the processor throttling that is advertised is supported in Ubuntu...?
In the end I am quite happy with this laptop. I think it's a nice looking, high spec machine for the price. The battery life and speakers are the only things holding it back for me.