LBS are fine for people that want a mechanic to do the work or cannot do it themselves. Purchasing the bike you want wherever you find it is fine but you will not be guaranteed service after the sale. There are all different kinds of shops out there. Personally I have never purchased or had serviced anything at a LBS. I will purchase some parts and accessories though. I like to build my own bikes and keep them maintained myself. That being said, I would consider buying a new bike from a large retailer like LLBean but would not need any service afterwards.