Here are some more bugs in weldments:
1. Insert part A into part B. Edit custom properties of part A. They do not update in part B. (to be confirmd by SW)
2. When you trim say two different size welment features with the same trim using a cut sweep or trim feature the resultant bodies appear under both weldment features. This creates problems in the cut list table. (to be confirmd by SW)
3. Solidworks runs very slow when using large weldments because the cutlist is constantly being updated. (Confirmed by SolidWorks).
Feel free to add your own.