I'm having a lot of trouble getting merge vertices to work in Maya 7.0.1. Today I was trying to connect two matching cylindrical poly objects (one was a duplicate of the other) using merge vertices. No matter what the distance setting, the merger only produced 48 (the original number of polys), 32 or 2 polygons. I finally got it working by combining the object via Polygons > Combine, and then doing the merge vertices. Is that the correct way of getting merge vertices to work, or am I just dealing with an annoying bug?