Let me preface by saying I am a huge fan of Chuck. It contained the right mix of comedy, drama, action, character development and nerdherd-iness.
If the producers knew what was coming in season 5 I am very disappointed that they went ahead with it. This season did such a disservice to Chuck as a franchise. I just feel the season was very forced, there was no flow. I would have stopped Chuck at the end of season 4 minus Grimes getting the intersect. If they had to go ahead with season 5 then I would have added some filler episodes and finished it up with Chuck versus the Baby when it ended with everyone having a special time together.
I wish I hadn't watched season 5 because Sarah's memory loss seemed like a betrayal. I wouldn't have been upset if this is how Battle Star Galactica ended but this is Chuck. As some reviewers have said when we re-watch Chuck and see all those special episodes where Sarah grows and falls in love with Chuck it will all be for nought. At the end of the day it was a sad and depressing end to a fantastic and mostly light hearted show.