I was just recently told meta data has minimal impact on search. I was a little surprised at that statement. Yes, according to the "List of Best and Worst practices for designing a high traffic website", meta data has lost some of it's power to influence.
8. Keywords in Meta Tags
According to the guys at Webconf.com:
"Less and less important, especially for Google. Yahoo! and MSN still rely on them, so if you are optimizing for Yahoo! or MSN, fill these tags properly. In any case, filling these tags properly will not hurt, so do it."
Since Google has approximately 60% of the search traffic, you could ignore the other 40%, but I'd not recommend doing that.
From an effort standpoint, meta data is relative easy to add and there is no evidence that it will harm you. As long as you're relevant to your keywords and not stuffing, you should be in the clear and see some benefits from your work.
Coming up: Keyword Proximity