This information applies to version(s): 3, 4
If you use DxO PhotoLab, then it is worthwhile to purchase DxO ViewPoint for a better workflow as it can be integrated as a plug-in palette. However, if you do not own, or plan to own, DxO PhotoLab then there is no reason to buy DxO ViewPoint as well as it will only be a duplicate of Perspective Efex.