When viewing the flights in "My Itineraries," choosing the Upgrade option from there shows me that I can upgrade all inbound segments (LAX-SFO, SFO-ORD redeye, ORD-ATL) for 15,000 miles. I'm tempted to do this as I have no other upgrade possibilities (CR1, 500-miler, etc) - from what I've read here on FT, upgrading with miles is a "paid upgrade" that would be confirmed at the time of "payment" and I wouldn't have to play the waiting game for it to clear, correct?

Would it seem worthwhile to spend the miles in this case? Or would I be better off purchasing some type of upgrade?

Edit to add: After reading the stickied link to seating on the 777, I've learned that the SFO-ORD segment is a domestic 2-class 777XA.

This depends. If there is confirmable upgrade space available you would be immediately confirmed in F. You might be waitlisted on some segments, in which case you do have to play the waiting game.

Thanks for the info...each of the segments have X2, X9, and X6 as their availability. So it looks to me like there is space available....given that the SFO-ORD leg is a redeye, I think it'd be worth the miles.