This is mostly just a bunch of links and personal notes.
"From even the greatest of horrors irony is seldom absent." — HP (Oops, that was Lovecraft, not Hewlett Packard. But still).
I installed Kubuntu 13.04 on it without ever booting the Win8 that came with it. Not that HP will pay me back for the unused licence, though. The only important thing is to disable the secure UEFI boot. In order to enter the BIOS setup, keep your finger on [Esc] immediately after turning the PC on as it boots very fast and without message.
The important BIOS options are in [System Configuration]:
BIOS options are minimal. If you exclude UEFI and drive boot order, there's basically nothing else. I wish there was for instance the possibility to encrypt the disk at the BIOS level. Fortunately Ubuntu can do this easily, but it's a small performance drop.
Since there's no CD/DVD player on this machine, I used an external USB DVD player in order to boot the KUbuntu install DVD. A properly configured USB key would have worked too. It installed in less than 10 minutes.
As for the hardware: EVERYTHING worked out of the box: wifi, bluetooth, ethernet, webcam, sleep mode... Kudo to Linux for that.
With Kubuntu 13.04, it takes 6 seconds to go from pressing the ON button to the encrypted disk prompt, 6 more seconds to get to the KDE user login and 6 more to get an empty standard session ready to roll.
The only problem indirectly related to Ubuntu is that if you need to update the Insyde BIOS, update the mSata SSD drive firmware or update the UEFI loader, all of which currently have updates available, HP only provides Win32 executables... I wrote to them and the only answer they repeat like parrots is 'reinstall Win8'. I tried searching the forums but the various methods I know and used on other brands don't work: booting in DOS (or FreeDOS) won't let you run them; no way to load them directly from the BIOS; no way to extract the binary firmware file and apply it with an external tool... I haven't tried running them from Wine (dangerous). The only way seems to be to install Windows temporarily (to a USB key or SD card maybe, knowing that Win7/8 won't allow that). I tried installing WinXP and Win2K without success: the former gives me a blue screen of death STOP 0x7B during the start of the CD and the latter hangs during the start of the CD, even trying multiple service pack versions. That sucks.
The full reference of this model is HP Spectre XT Ultrabook PC with a P/N C2L51UA#ABA, a system board ID of 1888, an quadcore Intel Core i5-3317U at 1.7GHz, 4Gb of RAM and F14 Insyde Bios which I'd like to upgrade.
The keyboard is backlit and enjoyable to type on, but that's the only good thing about it. The keyboard is messed up in the sense that they merged some keys; in particular, putting Home/End/PageUp/PageDn as [Fn][arrow keys] is particularly spiteful: you now have to use two hands to navigate a page of text ! Also the multimedia keys have priority over the function keys, but this can be reversed in the BIOS; the problem is that no colors mark the fact that you have to use [Fn] instead of [Shift]. On the plus side all the multimedia keys work in Ubuntu: volume, brightness, keyboard light, Wifi on/off...
Having only two USB plugs is a bit limiting; and only one is USB 3.0. The USB can power a device (charge your phone) even when the computer is off, even on battery if you say so in the BIOS. There's also an SD card reader (remember to sudo apt-get install exfat-fuse if you want to read SDXC cards).
Another thing I'm not crazy about is that all the activity LEDs are on the side and due to the tilted shape of the frame, you cannot see them while using the machine. This includes charging LED, power LED, disk activity LED, network LED, etc... All completely invisible unless you turn over the entire computer ! File that under 'dumb design'.
I was also negatively impressed by the weight: it's small and thin but feels quite heavy. In order to access any of the internal hardware you have to remove the bottom case (about 10 screws). The SSD is just a tiny board plugged into the mobo, so it is possible to upgrade to another mSATA card (not SATA !). The battery cannot be swapped without taking the cover apart and anyway looks very thin and fragile once out of the laptop: forget about hauling a spare battery with you. And the RAM is soldered on the mobo so you're screwed if you were thinking about upgrading it in a few years. On the plus side it's 1600 DDR3, so it's pretty slick. (*)
The resolution should be better nowadays, my 3 year old phone has a better one for crying out loud ! It only comes with the glossy screen (would have prefered matte) but is quite bright. And there won't ever be smears on it because it's not a touchscreen and I don't sneeze all that much. There's an HDMI port, but no VGA or DVI output, so it won't couple well with a projector.
The tiny fan is high-pitched but not very loud as some users have reported, even when stressed out. BIOS upgrade F15 supposedly makes it quieter. Battery life is good: an hour of use barely brings it down a notch.
After a year of use I still cannot use the buttonless trackpad properly: trying to click by either a single tap or by pushing the membrane down always result in a large motion of the pointer resulting in a click in the wrong place. It makes it almost useless. Either there is something wrong with the hardware or the driver. Trying to right-click is annoying to the extreme, and I haven't figured out how to center-click or click-and-hold or, god forbid, right-click-and-hold ! Another thing that makes me hate this trackpad is that it's raised, making it even easier to hit by chance while typing, fortunately there is kde-config-touchpad or syndaemon.
Actually there is something wrong with the touchpad and it's a grounding issue: if you hold your finger on it, the cursor jumps all over the place. But if at the same time you touch the body of the laptop with your other hand, it stops immediately. While on battery the problem goes away. Using a different power adapter solved the problem.
So overall: design 3/5, hardware quality 3/5, linux compatibility 5/5, HP support 2/5.
2014 update: about a year after purchase I tried to take it appart a 2nd time to clean up some dust as I could hear the fan on hot days. All the threads of the screws broke !!! All the bolts were screwed in metal nuts set in plastic and yes, they all broke and came loose within the plastic. Meaning that I had no way to open the case anymore: the nuts were running loosely, without being able to remove them. In many cases I had to drill and break the head of the bolts so I could open the case, making it impossible to close again. So now the case is kept close by tape. I guess this case is meant to be opened only once...
Another note: the reason I opened the case a 3rd time is because some tea spillage ruined the keyboard. I was able to find a replacement (not so cheap), but changing it is a pain: you need to take apart the entire computer. The instructions are here.