Newegg has built a great reputation for being one if the best online computer retailers in the USA. I have been using them for 10+ years with nothing but high regard for them.
Recently they have expanded their business to marjeting for 3rd party vendors. This unfortunately has given them some negative reputation because they cannot always control the quality and service if their 3rd party vendors. Their warranty, return & exchange policies for items sold by 3rd party vendors is also limited. Just like Amazon & Ebay be sure to read ALL the details prior to purchasing.
I love the Newegg iPhone App... better than Ebay's app.
I think Amazon is easier to deal with then Newegg when it comes to problems with a product or order. Also ive found amazon more willing to bend there rules and take a lose to keep there customers happy even when they technically dont have to. Where as about a year ago I had a problem with a MOBO and new-egg wouldn't replace it and I had to go through a long drawn out repair process with the manufacturer for a MOBO that never worked from day one.