I've made two purchases from Whiteflash totaling about $20k. Their consultants are top notch and walked me through picking a perfect diamond. They provide Sarin reports and Idealscope pictures so you can see the good and the bad of any diamond you consider.
I also utilized their design service to make a custom setting for an emerald cut diamond. They provided drawings for my approval and the finished product was breathtaking.
Their service and prices are fantastic, and I wouldn't hesitate to buy from them again