Very important.

• I want to be with someone I enjoy talking to.

• I admit that I couldn’t bring much to the sort of relationship where intelligence isn’t particularly important.

• Intelligence is heritable to a significant extent, which is important in case children are produced.

One downside (in a sense) is that this approach will probably lead to two very career-oriented people being together, which causes some problems.

Edit: I’m saying this as someone who is significantly above average on the sort of intelligence measured by SATs.