Among all online diamonds stores, Bluenile is listed in US, being featured in media the most, very successful jewelry online stores in US,  and yet attracted men who want to purchase engagement ring in big discount and comfortable way. All online diamond stores basically offer the same benefits and certificates with similar policies. Difference you may find is price, varieties, grace period for returns and ring resizing, user friendliness, additional shipment payments.  We hope that review below can give u a big picture of  Bluenile.

 Founded in: 1995, online stores evolved from 25 diamond retail stores.
Office: Based in Seatle.
Featured in: Digital Bling: Diamonds for Sale Online (npr); On Web, Workshops to Create One-of-a-Kind Gifts (The New York Times), Get A Diamond Deal Online (Kiplinger.com); Blue Nile Diamond Deals (Forbes); Sparkling Holiday Season (CNBC)
No. of diamonds online: Over 60,000 loose diamonds. Their single warehouse sells as much jewelry as nearly 200 stores combined. Given large inventories, Bluenile offers diamonds at prices that are often 30-35% lower than retail stores. 

 Blue nile in Forbes Nov 2009
  Technology: very straightforward, easy to understand. Suitable for mens.
Credibility: world’s largest online retailer of certified diamonds and fine jewelry.  Internet Retailer Magazine reports that Blue Nile is bigger than the next three largest online jewelers combined.
Money back guarantee: if you are not satisfied, you can get 100% refund or exchange within 30 days – no questions asked!
Buy Back Policy: No trade in
Shipping and payment: Free FedEx shipping in US and 42 international countries.
Financing: Bill me later -Enjoy no interest for up to 6 Months on orders over $500*
Ring Resize: Free within 30 days
Certificate: GIA and AGS only
C.E: No C.E.
Complaints: 13 complaints over past 36 months. (by BBB reviews.)

                               User friendliness          ★★★★★
                                Diamond variety         ★★★★★ 
                                Customer service        ★★★★★
                                On time delivery          ★★★★★ 
                               Information provided    ★★★★★ 
                                Technology                  ★★★★★
                                Overall                         ★★★★★

 Feedback: Given that more competitions coming out in online diamonds stores, many professionals and buyers perceived that the diamond price that Blueniles offer is slightly expensive than other similar online stores.