"Out-of-this-world experiences" vs. "out of this world experiences"

If I recall correctly, the hyphens allow you to create an adjective - in this case, out-of-this-world becomes an adjective for said experiences.

If you don't use the hyphens, this set of words can still be interpreted as an adjective, but it will be implicit, allowing the reader to hit an ambiguity.

Now then, out-of-this-world is one really awkward adjective nonetheless. It would be preferable to say "experiences that are out of this world".

This is so much easier to read regardless of the need for hyphens

Introducing the World Cup box from McDonald's: the meal filled with experiences that are out of this world.

That said. If it is out of this world, it is not related to an earthly World Cup I would think

Wikipedia ( http://en.wikipedia.org/wiki/Hyphen ; about one-third the way through the article) has one or two 'rules' I think should be rules:

Compound modifiers are groups of two or more words that jointly modify the meaning of another word.

When a compound modifier other than an adverb–adjective combination appears before a term, the compound modifier is often hyphenated to prevent misunderstanding, such as in American-football player or little-celebrated paintings. Without the hyphen, there is potential confusion about whether the writer means a "player of American football" or an "American player of football" and whether the writer means paintings that are 'little celebrated' or 'celebrated paintings' that are little.

Compound modifiers can extend to three or more words, as in ice-cream-flavored candy, and can be adverbial as well as adjectival (spine-tinglingly frightening).

However, if the compound is a familiar one, it is usually unhyphenated.

[bolding mine]

With better formatting:

Introducing the World Cup box from McDonald's:

the meal filled with out of this world experiences.

I think that the hyphens are unnecessary (and unwieldy).

There are 28.4 million Google hits for the exact string "out of this world", and the second is an inclusion in an idioms dictionary - it's easily perceived as unitary (a compound modifier).

I also think that the restructuring suggested by other answerers removes some of the punchiness from the attributive-position version, so I'd avoid it.

I really would recommend reading the other points Jon Hanna makes in his excellent post, linked to (two steps!) by Blessed Geek (above).