I'm of the mind that any targeted keyword is a good keyword. I don't much care for KEI numbers, or even looking at the competition level for any keyword, though this information has its place over the course of optimization and setting realistic expectations. But when it comes to finding which keywords to optimize and which keywords to leave out, I'm of the opinion that if it brings targeted traffic its a keyword worth optimizing for.

Don't mistake that as an endorsement to optimize for only for high-volume, high-competition keywords, forsaking all others. That's a recipe for disaster for most sites, but one should not be "scared off" from targeting certain keywords just because they are more competitive.

There is also a lot of talk about targeting the long-tail of keywords. I'm all for that as some studies have shown that these keywords often produce the bulk (if not at least half) of the traffic and sales a site receives. But the long-tail keywords should not be a replacement for the primary, high-traffic volume keywords either. I think a well balanced optimization campaign can and will go after both.