I know this thread is more than a year old, but I recently watched the movie while I loved the series and after reading the posts I agree with RepentantSky's post for the most part...
" This is supposed to be Japan, some 25 years before Excel Saga, which also seems to take place in pretty much the same universe ..."
I suppose you meant "Accel World". Excel Saga seems to be an entire different anime although I haven't watched either of them. But giving the fact that an SAO game is themed around Accel World I would say it is a really strong indicator. Especially if you consider that AW takes place in the time you mentioned while ES does not.
Asuna being a badass at the end of the movie is perfectly fine. She did not just fought in SAO, but in ALO as well. Hell, the most difficult fight in her entire life, against and with Sekken aka Yuuki, was in New Aincrad of ALO, not neccessarily in SAO. So whiping clean all thouse memories by just targeting the ones of SAO is close to impossible at best.
My biggest problem with the movie however are the villans. In fact after reflecting their motives and actions I head real headache. Adding to the point above of not caring fore people dying in the end while claiming to act benefitial to the SAO survivors, why the hell did they wanted the memory of SAO players in the first place? For the less than 2 years - depending on how early Yuna died in SAO - of memories of her that most of those people don't have to begin with? What a retarded move is that? The father should know her better and for a much longer period of time than anyone in the entire world and yet he wants the memory 6,000 SAO survivors? Why not scanning his memories instead? And even if he wanted to add that time she spent in SAO to what he could have contribute, why go for such extreme measures?
On a side note: the idea of stealing memories is bullshit to begin with. Memories are data, data can be read and copied without erasing or damaging it. The human brain is no difference, just a bit more complicated. But if he is able to read the human memory and able to process that data a simple and continuous scan of those areas would not only decrease the suspicion of something fishy going on, it would also achieve more reliable data about Yuna without causing any damage to the brain at all. And it would have given the story authors more room to make the enemies more relateable than a bunch of moronic hypcrites that they are. Or maybe even introduced an interesting plot twist.
But, if you don't think about the plot and just enjoy the VFX, you will not be disappointed - at least compared to the anime series.