If you take pics at night, then OIS is far from a gimmick.
If you have ever had blurry pictures because of an unsteady hand, then OIS is far from a gimmick.
If you've ever filmed video with your cell phone, but didn't like how jittery it turned out, OIS is far from a gimmick.
If you don't like buying special gloves to work with a phone, then Pureview HD+ isn't a gimmick.
If you've ever hated the blur that occurs in some action movies when viewing on your phone, then Pureview HD+ isn't a gimmick.
If you've ever tried using a phone outside in the sun, then Pureview HD+ isn't a gimmick.
HOWEVER... other than that, it's totally a gimmick.
Sorry to say, but every OEM is equally guilty of the "gimmicks". Nokia has their camera, and HTC has their Beats Audio. I'm not trying to play sides here, but to give opposition equal time, I have a 4 year old son & a 1 1/2 year old daughter...safe to assume I takes lots of pictures of them. Currently, I sport an HTC TITAN, and to be honest, I have never had to worry about a blurry picture, or shaky video.
My TITAN's camera performs just fine for capturing every moment of my children's lives...it's actually better than my wife's Lumia 900, even after the 7.5 refresh update. Unless I ever have to take a video of my children riding a bike next to my moving vehicle, I don't feel the "need" to purchase a Lumia over any other OEM.
Like I said, everyone has their gimmicks...if you want OIS on your camera phone, get a Lumia. If you want built-in amplifiers on your phone, get an HTC...and if you want what everyone thinks is the answer to all of life's questions, get a stupid iPhone.