[herewulf]

It probably compares very similarly to the German dialect situation in that it is a dialect continuum. The dialects become less intelligible as geographic distance increases.

The article alludes to this at the end:

"Romance linguistics teaches that by walking across the former Roman Empire from Sicily to Normandy, every pair of neighboring villages can understand each other."

"Language" vs. "dialect" is also very tricky because politics often come into play to demarcate the two. The classic saying is that a language has an army and a navy whereas dialects do not (i.e.: languages are associated with nation states).

And the classic example is that of Norwegian, Danish, Swedish which due to high mutual intelligibility are often linguistically thought of as dialects of one language. However, each one belongs to a nation state whose inhabitants would likely often disagree that they speak "a mere dialect".

Edit: Stepped away from the computer for a long while before actually posting, hence the similarity to the answer below.