Are keyword Meta-Tags still relevant?

The answer is "yes" & "no".

Google has discontinued including the keyword Meta-Tags contents in its SEO Rankings algorithms.

The other primary Search Engines, Yahoo and Bing still appear to include them in their Indexing and Rankings algorithms, as long as they are supported by wording content on the respective pages.

So while keyword Meta-Tags do not make a significant difference for Rankings, they do not cause any harm, as long as they are supported by relevant wording contents.

Just a word to the wise...