Build Your Own PC vs A Pre-Built PC?

http://chris.pirillo.com/ - When I opened up the virtual floor for your questions (as announced on http://www.facebook.com/chrispirillo and http://twitter.com/ChrisPirillo if you're not already following me there): one of you asked this question. What's the value in building your own computer versus getting one off-the-shelf, pre-built?

My PCs seem to be happier if I let someone else assemble and mitigate issues before I have to face them. Sometimes, I just need to save time in life - not waste it.