I've been using a Surface Pro 3 for a few days. I bought it to eventually replace my laptop of 4 years, a ThinkPad W500 running Linux (Ubuntu, then Linux Mint Debian Edition).

For now I'm using it with Windows 8.1, and Ubuntu under VirtualBox. Supposedly Hyper-V would run faster but it disables Connected Standby so I'm sticking with VirtualBox until I get around to installing Ubuntu for dual-boot.

First thing I did in Windows was disable indexing and other background processes and it runs quiet and just warm most of the time (i7, 8GB RAM, 512 GB SSD). I'm happy with it in this aspect, the fan comes up some times but so does the W500, and the noise is much less intrusive. The T41 and W500 I've used have an annoying "yaauuuuuuuuuuuuuuuuu" sound, worse for the T41 in my recollection, but the Surface has a constant white noise that bothers me much less.

Then I installed Firefox, GIMP, Inkscape, Blender, and Emacs. They work very well. Still no pressure sensitivity in GIMP, even after installing N-Trig's WinTab drivers, both 64 and 32 bit versions, so I would not lose anything by using them under Linux, but the graphics under VirtualBox is quite slow, even with 3D acceleration enabled.

The pen is very accurate, the smaller parallax compared to Wacom helps in using it as a mouse, but for freehand drawing it's still worse, compared to a Wacom Intuos 3 (external USB) and to a Samsung Galaxy Note 10.1 2014 edition. I tried using the Galaxy Note as my main computer since I'm compiling in remote machines most of the time anyway, but I'm very disappointed with Android. Linux console applications work fine after you install one of the Debian chroots, but I've tried a GIMP-Inkscape-Xserver[1] bundle app for Android and the re-drawing is uselessly slow.

[1] https://play.google.com/store/apps/details?id=org.gimp.inksc...

The biggest problem with the pen, now that pressure curves can be adjusted, is the wavy diagonal lines. This is not visible at 1:1 zoom, but when drawing freehand in Inkscape, when you zoom in it's absolutely obvious and you need to adjust the spline handles everywhere. I normally draw curves by adding the points one by one though, so for me it's fine.

I find the type cover excellent given the constraints. It's not as good as the W500, sure, but it's good enough for constant writing and programming with Emacs. It's better than the ThinkPad Tablet Folio Keyboard (USB) that I modified to remove the cover part. I'm considering getting a ThinkPad Compact USB keyboard because some of my usage involves positioning the tablet as a monitor, separated from the keyboard.

The touch screen is great and it's surprisingly easy to use normal applications just with your fingers. Not great, but I find it much more accurate than the Galaxy Note.

I've tried other combinations before to have both a retina-class display and Linux in a portable package: Toshiba AC-100 with Lubuntu + iPad 3 which was OK for LaTeX and then visualizing and browsing in the iPad, Samsung Chromebook 3 (ARM) + iPad which was an improvement for browsing on the laptop and console use (Ubuntu with crouton) and still allowed me to use LUKS encrypted external storage which Android doesn't, then Galaxy Note 10.1 with Debian chroot as mentioned above, and now the Surface.

My impression is that once I get it to boot in Linux with the type cover [2], bluetooth and 5GHz WiFi working it'll finally cover all my needs.

[2] there is a kernel patch already for it