Sexual attraction and compatibility are two different things.
I believe some attraction is important. But you don't necessarily have to have butterflies in your stomach every time you look at your SO.
Compatibility comes with the relationship as you learn about one another's bodies and explore things together. This takes TIME. That is why, in a HEALTHY marriage, sex actually gets better as time goes on.
Putting so much emphasis on sex is a bad idea. First of all, sex is better with someone when you've actually "practiced" together. So, thinking you can try someone out to see if your compatible is a loser's bet.
Second, a real commitment to someone means that you stick with them through thick and thin. If a relationship is based on sex, then what happens when an illness or an injury makes your SO unable to perform in bed? Are you just going to drop him or her?
In the long run, something other than sex must keep a couple together. Mutual interests help, and I would choose those over "compatibility". But, ultimately, it is about growing together and being committed. That encompasses everything - the physical relationship, shared interests, and a willingness to help the other person grow and discover new things as well.