I do not model in triangles specifically because quads make weight painting easier than triangles, but every mesh that I import is automatically triangulated in CC4. This and the automatic Tesselation make it difficult to accurately weight paint in CC3. Because it's triangulated, you can no longer select loops which makes weight painting way more difficult than necessary. I would like to suggest that when a model is being imported, that you leave it in quads, whereby you can use loop select to help make weighting easier. Once the weight painting is done, you can add a finalize step which then does the triangulation needed.