Just finished watching this - only took me ten years.
It's good for the most part, but the pacing is terribly uneven. It ploughs through six volumes of light novels in 24 episodes, but some of them take up six full episodes, while one is dispatched in just two. And because of that the story never entirely jells. (Also partly because the story is complete nonsense.) The first arc - which is given the most time - definitely works the best, but even that is somewhat rushed.
Those quibbles aside, they do manage to do many things well. Every character in the rather busy opening credits is shown, fleshed out, and placed in context in the respective halves of this first series. Except for the maid girl, who is mostly still just a caricature, and Uiharu and Saten, who are major characters in Railgun but I don't recall ever seeing in Index, not even in the background.
Onwards and Railgunwards!
Don't recall any pengis, though. Sorry. Here are some substitute pengis for you.