Yup, of course I've heard of it.
In fact... IMO, neffy is not better.
Yes, neffy is like 1/3 of the cost of the 3m vinyl.
BUT, neffy does not have adhesive backing, therefore, additional adhesive is required, that means, when applying, to repeel and re-use the same bit of material will become a problem. Not only that, after being applied, if you want to peel it off, that might become a problem as adhesive was used to secure it. Where as with the 3m vinyl, it's got self adhesive backing, you can peel off and re-use it as many times as you like (well pretty much), if it gets all creased, use a heat gun and boom! it returns to how it was before you even started. Or if it starts to lose the stickiness due to dust or oil, you can just wash it off with soapy water and it will stick again. Also the 3m self adhesive is easily reversible, just heat it up a little bit with a heat gun and off it peels.
Apart from that, the 3m vinyl has a gurranteed 4 years lifespan outdoor with UV protection and 12 years indoor, while the neffy does not offer UV protection and its not recommended for outdoor usage. And as much as you say you use it for interior (indoor), there will always be sun (UV) shinning in from your windows.