Substitute for butter

I think that would be a contradiction in terms. Most margarines aren't much better in terms of fat content, and some you can't use in the same way as butter.

Most low fat spreads are just oil mixed with gelatine and water, so upon cooking it just turns to water. The only option with butter subs, is to use less, or go for a healthier oil- one with less saturated fats. Some would prefer a scrape of butter rather than a lot of crap tasting low fat spread