As for replacing your ubuntu machine, the default distro is 12.04, but I'm sure you can install the latest.
I don't know about the amount of shell tabs you can have (as I use tmux), but my short experiment seems to hold up well.
The only problems I think you'll face is the scary 'OS Verification' at startup and limited memory (but can be solved by using a SD card). croutons are cheap to install so install, remove, install until you find your niche.
Oh , I think there is a misunderstanding going on here , Maybe I describe it in bad way , By replacing I didn't mean installing ubuntu on chromebook , I just want switch away from this whole gtk/qt/unity/gnome/kde/xfce/cinnamon/mate non-sense.
Main thing I am looking for is how is crosh , when you using it in heavy way (gcc,emacs etc).
You can also install a chroot with the cli-extra target. This launches the chroot in a TTY with the `sudo startcli` command from the crosh shell. Instead of launching into a desktop environment.
Then I just startup a ssh server there. And head back to ChromeOS and SSH to local host (the secure shell plugin is good for this). This means my chroot is totally independent of any chromeos windows or crosh shells.
I run a window manager with a full-screen xterm that has my tmux session. My packages are installed in a chroot that uses either Ubuntu 14.04 or 14.10 (I don't remember exactly, on a different machine right now) using Crouton. This was better for me since I have a non-trivial xmodmaprc that I prefer.
As for replacing your ubuntu machine, the default distro is 12.04, but I'm sure you can install the latest.
I don't know about the amount of shell tabs you can have (as I use tmux), but my short experiment seems to hold up well.
The only problems I think you'll face is the scary 'OS Verification' at startup and limited memory (but can be solved by using a SD card). croutons are cheap to install so install, remove, install until you find your niche.