Well, I hesitate to add to the me too chorus -- but yes, these folks are great.
The venting and plumbing for our water heaters and radiant floor heat system were poorly done by the original builder. A complete mess. We hired Bay Area Plumbing and Heating out of San Carlos -- and they made it worse stringing us out over several months! (You can search for my review of them for details). We were finally referred to Simms, and boy, do I wish we had found them first.
The initial tech Elias came out and diagnosed a bad water hammer issue in less than 30 minutes. He completed much of the fix right then in about 2 hours. We was extremely knowledgeable, respectful of our home, efficient and explained things very clearly. The next day he came back with his boss, Steve Simms, and they further diagnosed all that was wrong with our stupid system and how the previous plumber had mangled it further.
We also had an unrelated jacuzzi tub issue that Elias went through Herculean efforts to fix -- it was an impossibly tight squeeze were a tube had been severed by a rat, and he persisted until he finally was able to thread the new tube.
In just a few days of having called these guys, they were able to diagnose and fix everything. Steve also provided us with a thorough write-up that we could use to get some money back from the prior plumber.
Veronica, the office manager, was also extremely friendly and helpful in getting us squared away with prompt appointments and the write-up.
My only two complaints are that they do not accept credit cards and that the invoice/write-up took a little longer than we would have liked (but completely understandable because it was around the Thanksgiving holiday).
Overall, a highly competent, prompt and ethical contractor. We will definitely call on them for future needs.