Danny and I have been playing multi for 25 years. We play it because we like it and like the alternative uses for 2♥ and 2♠. It's also fun to play.
We don't play it "just to mess up the opponents" as some have opined. Of course any destructive bid has the potential to cause heartburn. Consider 1♣ - 2♥ showing both majors which is very popular these days and can be done with a zero count opposite a 10 point opener .
Most of the times that the opponents have gotten bad results from playing against multi are due to the misuse/misread of the ACBL defenses. Consider these real life situations.
None of these disasters would have occurred without the ACBL authorized defenses. The pair playing regular Lebenshol would have know that 3♦ was a signoff. The other player would have never bid 3♦ without being handed the book. It would have been much better for the opponents to just use common sense and meta agreements.
IMO the books have got to go. There is some discussion of allowing players to use their own written defenses in lieu of something provided by the ACBL. I have no objection to that approach as long as players are at least somewhat familiar with them when they come to the table.
FWIW allowing more multi rather than severely restricting it as the ACBL has chosen to do would eliminate the problem all together. Since players would quickly get used to playing against it just like all the club players in other countries.
Plus... it's free!