I liked the entire series TBH, but I'm not a giga fan of Star Wars in general. Reva annoyed me at the start (probably intentional) and I don't think her story ended up being all the great at the end. I'm sure if they do a second season they could advance her character. Personally think the other inquisitors took away from her story, or weren't all that necessary to the plot.
At the end of the day it was a cool nod to Obi-Wan getting his mojo back and then learning to communicate with Qui-Gon at the end. I know some people probably didn't like it but I liked the entire Leia arc. Not that she wouldn't turn out that way anyway, but I guess it pushes her a bit more in the direction of wanting to become a great leader.
The whole Vader fight scene was cool, wish it was a bit longer though. To me Vader loses to Obi-Wan again for the same reasons he lost to his son in RoTJ. He's conflicted and from what little I know about the comics and other sources of media this is something that happens to him constantly. His lines read like a lie to himself, the same lie he told himself constantly during RoTJ.
Obi-Wan not killing Anakin, even if he acknowledges him as Vader at the end is certainly in character for him. I think he was just too heartbroken to kill what he essentially believed to be his brother. Also Vader leaving people alive seems oddly in character (at least to me) in this series. It points out multiple times that's he's too concerned with winning and pleasing others, so leaving Reva alive when Obi-Wan is literally a breath away makes sense to me. The cold ruthless Vader we see is more apparent when obstacles like Obi-Wan aren't staring him in the face.
I think there's room for another series but seeing Vader interact with Obi-Wan again would probably diminish the entire appeal. From what I've heard I think Darth Maul makes a re-appearance at some point, which could be the antagonist of that series (with more elements interwoven). Vader would just need his entire own series though which would be bad ass.
One of the cool things about the series (especially the last few episodes) was just seeing the force used more, which you don't see all that much in the prequel or original series.