There wasn't quite as much action as I was hoping for/expecting, coming off of Index, but the big action sequences are AWESOME! And the more slice-of-life-y parts aren't bad either, really. Oddly enough, though this series gives a lot more focus to characters than plot compared to Index, the plot is actually a lot more coherent and solid. Where Index is more a collection of short stories with hardly any connecting threads besides the characters involved, Railgun fits each story arc seamlessly into a broad, overarching meta-plot.
One thing that really stood out to me about this series, especially as compared to Index, was the music. The OPs, EDs, and soundtrack for Index were decent, but nothing fantastic. Railgun, on the other hand...wow! The first OP in particular, "Only my Railgun", is phenomenal -- and when you hear it coming in during a climactic battle, the effect is just breathtaking.

All in all, I'd say this side story actually *just* edges out the original story it's based on in my book. And considering that I thought Index was pretty damn good in the first place, that means this is an absolute must-see.

Wow! At first I was skeptical about going back to Academy City without focusing on Index, but this show easily outpaced and outshown its predecessor. Mikoto's character was really allowed to bloom. Shirai makes a slam early on as heavy comic relief, but fills out wonderfully as a well-rounded character. The inclusions of Uiharu and Saten really added so much more to the story, I doubt it would have been half as enjoyable without them. And now the whole Academy City setting introduced in Index feels much more real and complex.

The story builds on itself intricately, with smaller archs playing into the larger ones, until the entire plot interconnects at the end. There seems to be a few side and filler stories, but it's surprising how even those episodes that seem to be incidental end up playing crucial roles in the huge climax. And the climax IS huge. It does not let you down. It's a great story told well from start to finish, and how often can you say that about a show?

Beautiful art style. The music is ass-kicking. Best of all, there's plenty of opportunity to go back to Academy City and tell more stories. I can't imagine there not being another series eventually, but until then, I'll wait for the DVDs. This one's a winner!