Lots of people have used it, as have I. It works great as long as you carefully follow the directions.
Key points...
Don't let it warm up or freeze. Keep it cool right up until you use it.
You add the Bio-Spira to a tank at the same time you add the fish. Instant cycle. No need to add ammonia or anything like that. You can use it in a brand new tank or an established one where you are adding more fish.
Shake it WELL. The bacteria are all glued to the inside of the package, and need to be shaken loose.
No water changes for 48 hours to let the bacteria stick to things.
Good luck!