Something like a bivi bag may be a better option than a hammock. Most of the places I've ever camped wouldn't work with a hammock. As others have said, very few campsites have suitable trees, and even those who do, probably don't have them with the right spacing.
This means that you're really only going to be able to use it when wild camping, and even then many of the locations I've camped haven't had suitable trees. They would need to be reasonably robust, with roughly the right separation and not over the top of a mass of sharp undergrowth (or stinging nettles or similar).
Some of the bivi bags I've seen are comparable in weight to a small lightweight tent, so I think I'd stick with a small tent, such as the one you linked to. Bivis may have less poles than tents, but modern small tents generally only have a few light poles, and are more versatile.
My single man lightweight tent (admittedly more expensive than the linked one), a Laser Photon, weighs just under 1kg, although with some sensible tent pegs, and a footprint, this goes up slightly. Most bivi bags aren't much lighter than this, and some are heavier.
