Since starting this thread, I have added a Tower of Power gas controller, and am also using Blichmann's Top-Link software on a laptop to create mash profiles for the controller.
The gas controller works very well. It is simple to connect, and fairly brainless to use. It turns the gas on and off ignites the burner with an electric spark element when the system needs heat. Coolest thing it does is turn itself back on, literally in seconds, if the flame blows out from a gust of wind. It comes with a temp sensor which plugs into the system on the output side of the pump, on the way back up to the top of the mash.
There is a differential of several degrees between the measured temperature coming out of the lower kettle, and the actual mash temp inside the tun. On the 10 gallon system, Blichmann recommends starting with the 1.25 gallon/minute orifice in the tube coming out of the mash. Using that flow rate, the differential between measured temperature off the pump, and inside the mash, was about 8 degrees. I up-sized to the 1.5 gallon/minute orifice, and this differential came down to about 1-3 degrees. Once the mash settles into a temperature, maintaining a temperature for an hour, the differential went down to almost zero with the larger orifice. Doing this creates a little more suction on the mash and you need to watch out for a stuck mash. But I've done it now on three batches with zero issues. Just be sure you let the mash sit for the first 15 minutes as recommended, and avoid using a fine crush.
The latest addition to the system was the communication cable, and plugging into a laptop with Blichmann's Top-Link software. I first tried installing the software onto an old HP mini computer running XP. It installed but didn't run correctly...the on-screen buttons were missing. So it now runs on a larger HP Stream 11 running Win 8. Works perfectly. Creating a profile on the software is easy but I suggest you view the videos on Blichmann's site to see how the program runs. I used it to create a mash profile for a Saison using the Saison Dupont mash profile described in Farmhouse Ales. It is a continuously rising mash starting at 113 degrees and rising to 162 over 1:45. This gives an increase rate of about .5 degree per minute. Send the profile to the device using the software, run it, and by golly...it worked absolutely perfectly to turn the burner off and on about three times a minute, gently ramping the temp from 113 to 162 degrees over the hour and 45 minutes.
At any time, you can stop running the profile and return the controller to manual control, or just use the device's panel to enter a new target temperature if you want.
The software lets you save profiles for later use, and it also has an option to graph the progress of your mash for later viewing, if you want to tweak it for future batches. One thing which seems like a glitch, is when I went to the graphing option, then closed out and went back to the main screen, the program closed down. Opening it back up, and the same mash profile was still running and picked up where it left off. Actually, the videos say that once you send a profile to the device and run it, the controller is doing the work and the desktop software is just monitoring it. But stopping the profile on the desktop, or turning the switch on the device to On or Reset will also stop the profile from running on the device.