It was plastered on but it is probably better than Index, well, it is when it isn't slice of life eps with the **** brigade. Railgun plot/action eps are usually fun. Sisters arc was done so much better in Railgun than it was Index. I guess it does lack punching though.
First series was mostly slice of life stuff with a couple of arcs. I liked the last arc final fight thing. The series airing now has redone the Sisters arc and Touma vs Accelerator stuff, much better than in Index. Can't say I'd suggest it because i've seen hundreds of better things but it isn't awful.
'tis just a bunch of exaggerated personalities having wacky fun times. Fun things are fun. I'm not going to psychoanalyse an Oreimo characters because that would be silly but yeah, the series is about the person in the title getting the happy end.