As a current PhD student in CS -- seconded. I'm fortunate to have a great advisor, and my research career so far has been largely fun and productive as a result. I have also seen equally (or more) talented and hard-working students have worse experiences because of worse advisors. It's just hard to become a good researcher without good mentorship.

As far as practical advice for finding good advisors, track records of previous students can be a helpful first filter once you've made a list of people who wrote papers you like. Probably the most helpful thing is talking to current students at the admitted students day and listening to them. Bad advisors usually have at least one notable case, and there will probably be at least one person who'll take you aside and tell you about it. Listen to them carefully. Even great advisors can have at least one unsuccessful and bitter student through no fault of their own...but they usually don't show up to the admitted student events unless there's a real cause for animus.