I've just installed LyX 2.0.5 (Windows Vista).
The updating of View Source is a definite plus, with only the relevant
formats now listed in the Format box, and both LyX's own format and
plain text included in the options -- both of which I nagged for, so
thank you.
However I note that if I select, say, plain text in the Format box, and
then move the focus back to the main window, the entry in the Format box
immediately jumps back to Default, even though it is still plain text
being shown in the "LaTeX Source" window. This looks like a (little) bug
to me. (And is "LaTeX Source" the right name? Perhaps just "Source" or
"Source Code"? It is after all "View Source" rather than "View LaTeX
Source" in the menu.)
One reason for wanting plain text to be included in the View Source
formats was that there are little surprises in what emerges as plain
text. Being able to look at View Source gives a means of checking that
all is as expected. For instance section numbers are retained in plain
text but chapter and part numbers are not. (Why?) I tripped on this
earlier in the year when working on editing bibliographies in LyX.
Andrew