I believe lust, regardless of what people want to think, is the initial start of any relationship. I believe people are often, first attracted to each other in a lustful way and then love is formed. I think love is an important emotion and experience that people must experience and be aware of.
Healthy lust is simply understanding when you find another person attractive. It can be a good tool in helping you determine what you find attractive in a potential partner, as long as you do not allow your lust to grow into an unhealthy obsession. Lust is, therefore, a very important step in finding love and, thus, every bit as important.
I have experienced love without the initial first step: Lust. It was very pure, and different. It has nothing to do with looks. Love starts from friendship, and the meaning of "love" is to care about someone. It's very pure and I wish people would understand that but they don't.
I don't think lust is a sin, but it's more temporary. Love is important. Liking someone is a bit of a healthier way of starting a relationship. Like is feeling good around someone. Liking someone is very helpful because it can end up as love. Most relationships start out with "puppy love."