It's not a SSRI - it is a benzodiazepine (like valium). It works fast on anxiety. It is effective at controlling the symptoms. With daily use over a long period, there is a possibility of dependence. For occasional use, not so much of a concern (most people with anxiety have anxiety over becoming dependent and they self-regulate). Can cause drowsiness. Don't mix with alcohol.
Good for helping breaking a cycle of anxiety, but xanax itself is usually not enough for long term treatment.
As I see it, anxiety involves an alarm bell going off in the brain. This type of drug is good at temporarily disconnecting the alarm bell. But it does not deal with the issues that make the alarm go off in the first place. Exercise, cognitive-behavioral work, diet, and meditation/prayer should be considered along with the xanax for dealing with anxiety.