We've owned ours for about two months so far, and we love it.
We wanted to stop buying bottled unflavored sparkling mineral water, and I did the math and determined it was going to be cost-effective to get the machine and make our own soda water.
The machine is dead simple to use, and the ability to select the level of carbonation is a thoughtful idea. I was a bit surprised it doesn't even need any electrical power for the carbonation to work.
However, there is a 3 element LED that shows you the level of carbonation you're getting, and that's powered by a "non-user replaceable" battery. This is probably the only con about this machine. According to the user's manual, you have to return the machine back to the company to replace the battery.
But the good news is that there are videos available on YouTube that show you how to replace the battery by DIY means. It's a bit of a hassle, but you should be able to do it if you know how to use a screwdriver.
Also, if you're going to get one of these machines, make sure to budget for about an additional $20 to get a two pack set of one liter bottles. One liter is not a whole lot of liquid (it's about the size of a 32oz. Big Gulp), and two people can easily go through one bottle per sitting. Three bottles (one comes with this machine) is probably a minimum, and probably four is ideal for a household with two adults who like to drink soda water to hydrate.