Look - as a pure dive operator, I'd say they were fine. The guides were decent and the equipment was fine (except for the comical gloves they give you that are like children's mittens rather than actual diving gloves).
However, one of the biggest challenges of going to the Galapagos is planning your trip. In this respect, scuba iguana gets an F. They were completely unresponsive over email, did not reply to my questions, quoted me different prices, and when I finally made the payment online, not only did they not confirm my booking as I had requested, they told me I paid the wrong amount when I showed up to the shop.
During our visit, we never had information from them about where to go (for non-dive activities, they use 3rd party operators). Despite numerous requests, they didn't give us the information we needed about our activities. They also changed our dive sites at the last minute to Gordon Rocks, without a disclaimer that you need at least 30 dives (my girlfriend is a new diver and was very uncomfortable in the strong currents and was upset we hadn't been properly warned).
Again, purely as a dive shop they were ok (although would it kill them to serve a little fruit or croissants or any food in the morning? It's not easy to find breakfast on the island at 7am, and we didn't get lunch until 2pm). But as far as planning dives and other activities on the islands, they were terrible and I'd stay away.