Personally, I've always regarded the IMC rating as a 'get you home service' rather than carte blanche to go plunging about in a light single in unsuitable weather.
Prehaps a little over cautious for some and maybe not for others. With just 15hrs of training you may or may not feel comfortable with the idea of flying into the grey yonder. I was lucky enough to be able to much of my training in real IMC so I am quite than happy to depart knowing that a portion of my journey will be in cloud.