Having recently joined the SodaStream revolution myself, I thought I would offer some revews and advice to those who are looking to purchase a Soda Stream or similar product. So far, I'm very pleased with my (2) Soda Stream devices and have some information that may well help you decided which product to buy.
From what I can see, the SodaStream Brand offers three or four basic models from which to choose. Each one adds a little more to the feature set than the one below it in their line up. But some of them are just the same machine in different housings, offering some style choices for the user. Here are some examples:
According to their website: "The Genesis soda maker is based on modern slim-line design which looks beautiful in any kitchen, and is a great choice for small kitchens. Among the Genesis features are: automatic access gas release mechanism, an attractive and unique color variety, a clever design ensuring minimum space taken on work top, customized carbonation level, and and easy to clean drip tray."
I own a Genesis and find it to be a good basic unit. It has some lighted indicators on the front to show you the level of gassification in the water so you'll know when you have enough, but as most of the models do, you can tell when it's at maximum level by the screaming sound of CO2 escaping from the unit. The thing I like about it is that it is basic and does everything you need. The thing I don't particularly care for is that you have to screw the bottle in each time to use it, rather than having a bayonnet type mount.