Something interesting from reading Berg's volume 2 book on the Winaver, which contains a chunk on the 7 .. o-o Winaver. 8 Nf3 has never been meant to be critical, and still isn't. This has traditionally been because of a lot of extra sharp options black gets. What is interesting there is that this book is (I believe) the first reasonably modern text to examine a lot of blacks very sharp lines with a high powered computer/very strong GM etc.
Consqeuently perhaps notable how many of these ideas Berg doesn't really like - he doesn't really like 8 .. f5 9 ef Rxf6 10 Bg5 Nd7 or Qa5, and gives detailed reasons for the former.
The old Kindermann/Dirr idea of 8.. Qa5 ^ c4 seems to have survived intact. (If not credited to them

Since played by other people etc it seems.).
Black can also go 8.. Nbc6 of course, which is rather important due to the 8 Bd3 Nbc6 9 Nf3 move order. That then leads to the final alternative position which starts below.
Now here 11.. Rf7 is fine (and covered in some detail), but does seem like a tiny bit of a retreat back to 8.. f5 based ideas.
The 'fun' line starts with 11.. e5 when it seemingly comes down to evaluating this ending:
All known theory/from several games this. You can't analyse that out concretely and he doesn't try. He clearly doesn't like it terribly much for black though, while Watson did in PTF III. Any suggestions/ideas? Its a rather interesting position of course.
My (very humble) feelings, having played something like this three times (at a modest level), is that I'm not sure Berg is right to be worrying about blacks king - the pieces/black rook tend to get active enough that white has to take Q's off at some point - but I'm not hugely convinced about how attractive the resulting ending is for black.
It is relatively easy to see how whites kingside could end up somehow rolling over black, while its much less obvious how black can hope to win.
(The one win I did get was when white rather careleslly let me keep the d4 pawn alive. Otherwise a couple of games which held but with a bit of work involved.).
One thing I can remember not being sure about when analysing my win was whether black should actually even bother recapturing the pawn on d4. The white pawn on d4 really isn't doing anything terribly relevant to help white and it does make d5 a rather nice outpost for a piece/save a few tempi. Nothing that'd change the long term features of the position though.