If you can deal with living purely on web apps, ChromeOS does just fine. Things to note: no Office, no Skype, etc.
I have the C720 and it handles everything on the web without any issues.
You can usually find an Ubuntu install using Crouton, but I haven't had much need to yet. YMMV.
I picked up the C720 last week and have been using it extensively as my home PC.
I must be odd, but I don't need Office at home.
And I don't use Photoshop.
Those are the most oft cited misses on Chromebooks that I see; I confess I do miss Lightroom and my collection of Steam Games - but I use them rarely.
I just have the C720 docked to my PC's keyboard+mouse+monitor, so I treat it more like a "Chromebox".
It's fast enough for everything I've thrown at it... I really can't tell that I'm not on my i5-2500k when doing my normal stuff on it.
My main desktop rig uses ~ 70-75w at idle (browsing web) and about 95w when watching .mKV's.
The Chromebook uses ~8w during normal use, and 10w while watching the same .MKV.
(Undocked, it's more like 12-13W.)
It's also damn near silent - I thought my PC was quiet in my R4, but this Chromebook barely whispers the fan every once in awhile.
It isn't replacing my desktop ( I do use Lightroom weekly, and will want to play Steam collection a couple times a week ) - but for browsing the same forums over and over as I do, watching downloaded .AVI's/MKV's and streaming Netflix, it's great.
Edit: The Samsung Chromebooks use the ARM processors which have a diminished Linux experience. Read up on the differences between the ARM and Haswell based chromebooks/boxes if you are seriously consider it for Linux. There are some recent articles discussing the merits of the cheap Chromebook hardware for Linux, and there are many who say "If you want a laptop for Linux, just get a PC". (Which the ChromebookLinux fans say, "But ChromeOS is built on Linux and is inherently more compatible. Except for ARM.") But I'm happy at the moment just running the ChromeOS.