My understanding is that including devo max was seen as a way for the SNP to create a referendum that they could only win. And it wouldn't have put the question of independence to bed. Devo Max would have won and the prospect of an independence referendum in five years would have sat in the background.
Within the pro-independence community there were two ways of looking at Devo Max - second best or near enough to make no difference. This post at Peatworrier's blog pretty much covers it nicely, especially in the comments.
And, the 'close enough' side seem to have turned out right. What the SNP want seems to be a form of devo max dressed up as independence. Their formulation of Devo Max was for Scotland to be responsible for everything, with Westminster only handling foreign policy, financial regulation, monetary policy and the currency. What they propose as independence is Scotland controlling everything but in a currency union (which means Westminster regulating financial services, dealing with monetary policy and the currency) and shared foreign office and diplomatic services. So, a Devo Max option would have been a second, softer more easily won bite at the same cherry.
Another referendum? Depending on what the intention behind the Edinburgh Agreement was you can read the "decisive expression of the views of people in Scotland and a result that everyone will respect" as intending the referendum result to represent the "settled will", as Dewar called it or the "sovereign will" of the Scottish people, as we now seem to call it. Whatever the result, it's a done deal. No barriers to independence if it's Yes, but no Neverendum if it's No. If nothing else, another referendum would require another Section 30 order, which seems unlikely after this two-year marathon.