I am sure this issue has been addressed elsewhere but I would like to highlight one typical issue you will run into if you use 3D DWG instead of IFC when exchanging information with Tekla.
One of our users received 3D DWG export from the structural guys who are using Tekla for modelling/documentation. 3D DWG was inserted into a GM family and then loaded into a project. Everything worked fine until the user had to add some plan regions in plan views.
When you add plan region the entire GM family cuts at "A" plan region view range ignoring "View" view range. Technically this is because the entire structural model is one single 3D CAD block so it respects one view range only, whichever cuts higher.
To get around this issue use IFC file and everything works fine. Ok IFC may not be 100% perfect for a complete bIm scenario but at least for 3D collaboration point of view it is certainly 100% perfect.
More details on Tekla to Revit interoperability can be found here.