Best? Leon Mage... he does amazing non-pave pieces. Mark Morrel is also fabulous, however it depends on your definition of ''delicate'' -- his peices while fluid and stunning are more substantial than Leon''s.
I''ve never seen any of their pieces in person, but I''ve always been fascinated with their simple, flowing designs: http://www.niwaka.com/us/index.html
They''re a Japanese company, but according to their website, will open a 5th Avenue store in NYC sometime this year.