@Simkin I've only had the squid version, but it's definitely unpleasant to eat unless you have some alcohol (or soft drink) to wash it down with. From what I remember, it was firm squid strips sitting in a salty, sharp, funky, and bitter viscous liquid that coats your mouth when you eat it. It's just a bit too concentrated with all the flavors together (and why they only serve a very small dish of it), and you need the alcohol to help dilute/wash out/cut through it. Interesting enough, though, that I've ordered it again when I'm in a drinking mood. Probably not something to have on a date night, unless you're both feeling adventurous and you drink enough to get rid of the taste (on a related note, somehow garlic breath doesn't bother me).
Definitely not as bad as hákarl, where the smell is awful and the brennivín (which is tasty) doesn't help make it any better.