I have had octopus a few times, mainly marinated, and heaps of baby occies. Also had squid and cuttlefish. Deep fried S&P squid tentacles are so delicious!! They are my favourite item at dim sum!
Most of the occy, big and small, has been chewy - I have even had a baby octopus' head bounce off my plate when I tried to cut it and bounce to the floor below in the restaurant. Properly prepared and cooked it is really nice and tender. Simply prepared has always been the go, even when marinated. A lot of the marinated ones seem to have an issue with the chilli as the chilli doesn't seem to permeate the octopus, only the liquid so you get two tastes instead of one pleasantly flavoured occy.
Cuttlefish has only been in Chinese restaurants and I couldn't tell much between the squid and the cuttlefish, but that could have been the additional flavours.
Squid is the only one I have cooked myself, and apart from the ubiquitous squid rings (fresh, frozen, crumbed, marinated, etc), a very bad attempt at d/f squid tentacles, I have stuffed a squid with spinach and ricotta and covered in a tomato sauce for a slow cook in the oven. Squid you either cook very, very fast, or very, very slow. Ever only heard of octopus being cooked slowly though.
I think with all of them though, be thorough in your preparation, that can be a killer when you go to eat. Rick Stein I think cooked octopus in one of his series.
This was on tv here a while ago. It was prepared by a chef from a Tapas restaurant in Sydney (?), which I gather is meant to be the best in Australia for Tapas. Never heard of it personally before this show but other side of the country!
Pulpo alla Gallega (Gallician Octopus)
Here are another couple I recall seeing a while ago:
Amalfi coast - A Mediterranean recipe - Regional dishes
POLIPO AFFOGATO IN OLIO - OCTOPUS IN OIL