I am not much of a writer, but trying to make each forum a little more recent, so I will through this in here. I know alot of people here buy computer parts and build their own computers. I have recently built several for people and used NewEgg for almost everything.
Shipping: NewEgg had the order processed within a matter of hours and it was at my house in 3 days with most of the stuff, I think some things may have came on the fourth day.
RMA: Returning merchandise was no problem, I simply filled out an RMA and emailed me a form to put a RMA number on the package and then they arranged a UPS guy to pick it up free of charge and waived a restocking fee. The merchandise was fine, we just bought a cheaper monitor from Staples w/ a rebate (often really good deals there also).
Merchandise: The goods you can get at NewEgg are great. They have plenty of selection to choose from and brands you have heard of before. Sure there are cheap knockoff brands also, but its all up to what you feel like buying.
Packaging: Everything came in antistatic bags, and in its retail box if specified, and then was put in a larger box with more than enough bubblewrap and those popcorn foam things
Website: Great. Probably the best reason. You can see the prices and shipping immediately. You can add to cart and wishlist easily. The best thing is you can see ratings and reviews. It is nice so many users review things, b/c I am hesistant to buy much unless I have read a review (NewEgg links to external reviews) and the rating/reviews from actual customers.
Service: I mentioned service in a lot of other topics, but their phone customer service was great, low wait times, and very polite.
Prices: I have trouble beating any of their prices at any other reputable places on the internet. And doing the math, you can save a few bucks on this or that maybe, but if you are getting a large amount of merchandise, it is better to go here b/c you can save on shipping and its easier to track if you get everything from one spot. Plus, the extra few dollars on something (not the majority) is worth it considering the timeliness of fulfilling the order and the ease of RMA'ing anything.