so any idea if adding this to a MacBook Pro would actually benefit Lightroom and Photoshop? Historically they haven't played with GPU's very well.
Without seeing any numbers... my guess is that for Lightroom or Photoshop you will see not much benefit... if any... with an eGPU... like this one or with the boxes provided by other manufacturers. Specially if you elect the 560 gpu in the MacBook. The only scenario I see is that you want to drive more 4K/5k monitors (not sure how many extra this setup will allow).
For DaVinci Resolve users, they will see huge benefits. But careful if you are using Final Cut X, right now you need a hack to make it use the eGPU and this disables for the program the usage of the internal one... so less benefit. I suppose this will improve in the future versions now that Apple is going the eGPU way... no sure about premiere.
Anyway... the box is nice, quieter (although in full load the MacBook will make enough noise)... I will prefer to go the route of an Razer eGPU box that allows to upgrade the GPU in the future...
http://dgpfotografia.com