A bit early to tell conclusively yet as the OEM meters have not been received by their respective partners (ChromaPure or Spectracal) yet. They are due to start arriving within the week I understand. The ones used for testing so far are beta products.
But after saying that, I have seen the i1Display Pro retail product (can not be used for either ChromaPure or Spectracal), and the measuring window is a lot bigger when compared to the Chroma5, which will allow more light to the sensors, and thus give more consistent readings in darker shades of grayscale. It is also designed with non contact in mind, which may help 3D calibration. I am sure there will be alot more feedback coming to light as the month draws to the end, and the meters start to ship out to customers.