To help, imagine the following interaction model
(which we envisage but
it's not
a priority right now): in a wizard step, if the step form is invalid, the
"Next"
button is disabled (for example if the user has to make a selection, the
"Next"
button will only become enabled after the selection has been made). Now,
given
that the "Finish" button would be present on _all_ steps but disabled, I
think
it can become a little confusing for the user, who wouldn't know if there
is
something he needs to select, fill in, etc to enable it.
How about changing the name of the "Next" action at the end in
"Finish"
Prev Next
into
Prev Finish ?