The Ending -- and Miles' Novel (SPOILERS)
"Sideways" ends only after its protagonist, Miles, seems to have hit rock bottom: drinking his most precious bottle of wine in a fast food place; aware that the wife who left him is successfully, married and pregnant and that he is alone and unloved. (His "friend" Jack, seems to have disappeared from his life.)
And then he gets a letter -- via lovely voiceover -- from the beautiful Santa Barbara area waitress , Maya, who once loved him but rejected him -- not for his looks or his problems, but because he lied about his friend's cheating ways -- and she is interested in finally seeing him again. The movie ends with Miles knocking at Maya's door -- but we don't see what happens next. The end.
The "Sideways" ending is even more ambiguous than the "About Schmidt" ending in the movie that Alexander Payne gave us previously(hell,its the "Sopranos" ending, isn't it?)...but we can figure that Maya will be there, and will open the door, and that Miles has at least a CHANCE at some sort of relationship with Maya(friends? lovers? marriage?).
But here's something I think about the "Sideways" ending: Maya writes to Miles and offers a reconciliation because...she read Miles' unpublished novel manuscript, and it moved her with its autobiographical elements about Miles himself. And to me, that's sort of "the moral of the story": Miles could never sell that book for publication, but it is a good thing he wrote it....because MAYA read it ,and the book changed her mind about Miles.
Everything is worth doing...and what it WILL get you is sometimes a surprise. Miles writing that book is the proof.