I love ours! DH got it for Xmas last year and we use it all the time, I use the SS flavours and love the raspberry and cranberry lite, but TBH cordial is just as good and cheaper. The only hassle is refilling the bottle, it isn't as simple as just buying a new one, you have to go to places like Harvey Norman that actually can refill it for you. I think it is totally worth it if you like fizzy drinks (which I am a sucker for) and sweeties like cordial etc.
ETA: It is worth it if you aren't going to replace Coke, nothing replaces that, hidiously awful that it is for you, Cola flavours just don't cut it, so we buy others.