short answer is yes.

you don't want unused vertex creating n gons (polygons with more than 4 sides)
If your mesh has stray vertex and five or six sided polys then you will never really get a smooth mesh .
To get a smooth mesh you either a) convert your model to sub-division (modify/convert poly to sub-d) or
b) smooth the mesh under the polygons menu, if you have Maya 8 or later it's under the mesh menu. A word of warning though , if you smooth your mesh and then anytime after delete the history (modify/delete by type/history) you will not be able to return to the unsmoothered version.

On a final note regarding 4 sided clean meshes when you progress to rigging and animation you will find it very necessary to keep to these rules as binding and weighting a rig so it deforms your model in a natural looking way can be difficult if the mesh is not clean.

bottom line ...get into the habit it will help you in the end.