I'm not sure about Solidworks, but even the latest version of AutoCAD has no Retina display support. It looks a bit gnarly, and I generally wind up running it on an external monitor. If you use Bootcamp you can also just get the Windows version- it scales to lower resolutions pretty well (I use 1920x1200).
solidworks isnt even available for mac. i can run it fine (in windows through bootcamp) on my 13" pro though so dedicated gpu isnt a 100% necessity. will obviously be better though.