bash completion of apt-get

[Matthew K Grimes]

I'm a newbie to ubuntu and linux in general, but I have some experience 
with knoppix as a hard-drive installed system. One knoppix feature that 
I miss dearly in ubuntu is the tab-completion of apt-get packages. After 
some google research, I tried entering the line

[ "$PS1" -a -f /etc/bash_completion ] && . /etc/bash_completion

at the bottom of /etc/profile, then restarting, but this didn't help.

Another, unrelated question: How hazardous is it to add conventional 
debian mirrors and other deb sources to the sources.list file in 
practice? There are some packages not in the ubuntu mirrors that I need. 
If this is the case, should I just use some other debian distro before I 
break ubuntu, or is the risk of breakage minimal?

Thanks,
-- Matt