Depends on how you see it. Hyouka was misleading in a way that it made people thought that the show was about mystery. It's not. It's actually a slice of life that uses mystery to flesh out it's characters. Honestly all the mystery was quite lame, except for the origin of Hyouka. But it's why the mystery happen that makes it good. Anguish, jealousy, anger, manipulation, timidness, everything is based upon a logical human flaw. And KyoAni's way of using subtleness to show these works. Most scenes are brilliantly thought of, and you might miss some clues that alludes to a bigger picture the first time you watch it.
The last arc meanwhile was to expand the characters of both Oreki and Eru, and to hint on their everyday relationship that is not mentioned in the previous chapters (or episodes). It was also to show how both have grown, Eru, from an eccentric, curious, sheltered single child grew up to be a mature girl that understood her future, and Oreki who wants to maintain a grey coloured life, finally embraced a rose coloured one. Every interactions they made, people they met, actions they have taken leads to this end
Talking about the end, it was nicely done, staying true to the novel. They could have used an anime exclusive end that would have been a better choice in terms of the viewers, but that would actually disrespectful the the characters and their development, so they stuck with what Honobu has written. Throughout the show, it was shown that Oreki would digest all information that is given to him which will lead him to a solution befitting the problem (or mystery) that he has. In that last scene, the solution Oreki had from the information that Eru was giving him was to stay by her side, but it conflicted with his old lifestyle, hence why he never said it out loud. But he knew that it was the best solution for the both of their future. Eru ending the episode with "It's already spring" was quite subtle, and yet implied heavily of their future development. Their relationship is just starting. That rose coloured scene, the wind that suddenly blew and showed Oreki the beauty of the place, and that knowing smile at the end for me speaks volumes and is worth much more than an uttered line.

For those who wanna watch this for the mysteries, I suggest you to look elsewhere. This is a perfectly masked, slice-of-life anime.

Admit it. Just say you love the girls. All of them.