Has anyone switched to make their own (Sodastream / Soda Maker)?

I'm wondering about your experience with them:

• Have they replaced your seltzer/soda buying?
• How much do you use your equipment?
• Where do you get your CO_2 refilled and how much does it cost?
• What flavorings do you use and which are your favorite?
• What equipment did you buy and do you recommend it?