I've done skycouch with my partner, and while we're normal height, we're both pretty trim, and it wasn't amazing. However, if you buy the skycouch, you're guaranteed it! If you put in for a oneup, it'll be more than $600 for the both of you, and if it doesn't come through, you're stuck with economy. As oneups are at the bottom of the upgrade food chain, especially for 2 people, it could be a low-probability wager.

If you're both short or normal height and skinny, skycouch ain't that bad. Otherwise, save your $ (or make the bet on oneup).