What I love:
1) it's portable and needs no electricity
2) can customize carbonation level (4 pumps is my fav)
3) is super easy and fast to make carbonated water... So easy I was able to do it one handed while recording the video and so fast the longest part of the process is just filling up the water bottle before you carbonate!
I just have lemons and limes on hand and squeeze a little into a glass and boom, amazing and refreshing without having to go to the store!
My cartridge is still going strong so I haven't had to replace it yet but I've read they have an exchange program where you can bring the empty to one of their locations and get a free replacement (which is awesome!). If their isn't an exchange center near me they have an online program/mail delivery program and it's $16 to order your refill. They will send you a filled canister and a box with a prepaid return label to send back the old canister. With either option I'm still saving a ton over buying store bought carbonated water. Best Xmas gift I got this year!