Just wanted to share my opinion regarding purchasing your diamonds at JannPaul.
For the same specs and cut quality (i.e. Ideal to Ideal), you are definitely paying a premium over at JannPaul. I didn't want to be a sucker, so I ended up doing abit more work.
As most of you guys would already know, JannPaul emphasize that even among the GIA triple excellent diamonds, there are the "good ones" and "less good ones - in terms of Cut. So during the presentation, I asked the salesperson if there was any way to determine which are the "Grade 1" triple excellent and which are the lower grade triple excellent diamonds, based on the written specs/information from paper certificates. He said "No". This was after we did all the visual inspection through the normal scope and Ideal Scope and the Hearts and Arrows scope.
But through my own research and testing, I found this to be untrue. You can definitely determine if "a diamond" will pass all of JannPaul's visual/scope inspection from the specs of a diamond written in the certificate.
The criteria range for Ideal Cuts, as some of you all may have already known, are more stringent than the GIA triple excellent grading. The range for the cut depth, Table width, Crown, crown angle etc, have a smaller tolerance for the ideal cuts. For example, in an Ideal cut, your Depth must be between 58.5 - 62.5.
I asked the above question to the JannPaul salesperson because I wanted to know if the only way to obtain their standard of an excellent diamond was to carry the Ideal Scope set around different shops and inspect them myself. But apparently, that is not the only way. You can first filter the good ones out based on the specs listed on the GIA certs.
I was also told JannPaul cut most of their diamonds themselves. On average, their mark up on Ideal cut diamonds are about 20% - 25% more than another diamond of an identical cut (which will also pass ALL the visual tests of JannPaul).
So I would conclude by saying, yes, their services are pretty good, but be expected to pay a price premium for a diamond with an identical performance.
For me, I went with the option of looking elsewhere for an "Ideal Cut" diamond, first filtering by looking at the GIA certificates, and visually checking through the Ideal scope those diamonds which pass the paper specs . I saved myself slightly over $1k.