I take a yoga class three times a week and practice every night for an hour or so, but it's a program my instructor helps me with, not something I spend any extra money on (the classes are included with my Y membership, so they aren't any extra expense either).
If it's possible to become addicted to it, I have. It may or may not help you lose weight--that depends on the type of yoga you do, how long you do it, how often, and the effort you put into it--but it will certainly leave you more flexible, calmer, and more conscious of your body (in a good way, not in a self-conscious way).
I've found it also helps me
look as though I've lost weight. Great posture really helps with that. I've continued to lose weight through diet, and I walk and swim in addition to yoga, so it's hard to say how much it's helped with weight loss. It certainly hasn't hurt, though.