Higurashi Rei is the epilogue for the entire story. For those of you that are expecting more craziness, this isn't really the place to look for it as Kai had wrapped up everything properly. However, if you'd like to gain more insight into the world of Higurashi as well as deal with character introspection, check this out. It's best to think of this as a closing act. The first and fifth episode of the series are just slapstick comedy and don't bear any relevance-- they are just for fun.
In general, the story delves into the character's pasts a bit more, and comes up with a final scenario that questions the value of the struggle throughout the entire story. Despite the fact that the main story in the OVAs was very dialogue heavy I was able to reflect upon the series as a whole with Rika's thoughts and feelings. If the first season was about confusion, and the second season was about finding answers, this season would be about taking all of it for granted. Certainly that causes us to be a short time at times, even with all this knowledge?
Another strength of the story is that it provides more information about a certain ambiguous scene in Kai, and a possible link into Umineko, another anime that may or may not be linked to the series.
Visually, the anime is very impressive. It is an OVA after all, though I did prefer the character designs from Kai (the eyes are odd). The music is also a step above; the BGM seems more effective here. Superscription of Data is very impressive techno song, and Manzashi is an nice, soothing song that is suitable for ending the story, as well as serving as a complement to Taishou.a
I don't think these OVAs are for everyone. They may be too much talking for some people (but there's at least one side of Rika everyone needs to see), and the slapstick episodes are just kinda there. But if you liked Higurashi for the characters, there's no reason not to watch it.