Disadvantages are
1) the extreme foaming: When gargling, it is almost inevitable that the foam comes out of the mouth and runs down the whole neck and so can soil clothing!
2) the penetrating, strong "Bubblegum" flavor
3) a darkening of the teeth. Especially in combination with the toothpaste effect Meridol-halitosis products a slight darkening of the teeth. (Sort of an anti-Perlweiss.)
The price is not so bad - there are special (pseudo-medical) halitosis-conditioners that cost more than twice and appear much less.
Because of the disadvantages of the product has actually earned only 3 stars. However: There just is nothing else on the market, which works so well. In addition, the price is relatively moderate. Therefore 4 stars and a recommendation - with the hope that soon Meridol nachbessert.
UPDATE from 04:07:13:
I take the mouthwash remains and can confirm the 4 stars. Meanwhile I use the toothpaste Halitosis only to rub the tongue to reduce the blue / darkening of the teeth. (The mouthwash alone causes only a very slight staining.) The effectiveness of irrigation is good, but the extremely strong foaming on gargling remains very unsightly disadvantage.
Update from 04:09:14, reducing the rating to 3 stars:
From the mouse - now I use only the Halita mouthwash. I get the impression it works better than Meridol and has not the disadvantages.