tl;dr

My $.02 on the subject. I've been building bikes for an LBS for the past couple months,and have found numerous issues on brand new bikes that would be serious problems for anyone who isn't an experienced wrench with all the proper tools. You'd be surprised how often we pull out the hammer. Also note the fact that it's common for bikes to get messed up in shipping. Buying from an LBS means not having to deal with shipping and warranty claims right off the bat. Finally,shops have parts that you can buy now. You can get what you need on the way home from work rather than waiting days or paying extra for express shipping.