I used tortoisehg on Windows in the past, the GUI is very friendly.
Now i move on Ubuntu(11.10), i installed it using following command:
apt-get install mercurial python-nautilus tortoisehg
After the installation, i could use hg command, but i didn't know how to start the GUI(There was no related items in the right-click menu at all).
PS:I am using root account.
It looks like you run thg to do just about everything with Tortoisehg.
I strongly recommend not using root for everything. That makes it far to easy to accidentally shoot yourself in the foot. (If I had a dollar for every time I heard someone accidentally delete something really important because they were running as root, I'd have a good pile of tacos right now.)