Here is
a nice little 'beginners' article on dithering 
- the last two paragraphs sum it all up - still very interesting. So perfect polar alignment is not always a good thing if you don't have dithering software, like me.
Below is an example of what I have been told is associated with not dithering, called differential flexure. Polar alignment was particularly good on this occasion. So even DSLR users need to dither - and I thought that came with age.