Yes, I've used it extensively. It does work, but there are a few other components I've added to it based on individual child's needs. Do you have all of the materials - magnetic letter board, word cards, etc? Also, do you have Sounds Sensible, which is the downward extension of the program for teaching more basic phonics?
Also, SPIRE is very much a Direct Instruction (DI) program, which is more of a set of a methodology than a particular branded program. There are many DI-based programs - I'd consider SPIRE to be one of those.
We chose SPIRE after extensively looking at research and user reviews of SPIRE, Wilson, and a lot of others. For the price, usability, and efficacy, it's a good selection!