Our existing 2-zone controller is fast. I ordered this one hoping it would work and it did. Observations: 1) Requires a separate 24V AC power supply to operate. I purchased a 24V AC power supply from Home Depot (which sells sprinkler controls). So be sure to order one of these if you don't have one. Make sure you get one with the correct VA (amps) for your application. The manual has a fairly self-explanatory table of the size you'll need depending on how many external relays/solenoids/etc you need to power. 2) I really like that it doesn't require a tiny screwdriver to connect this device. Wire connections are made with spring loaded connectors. Nice touch 3) The circuit board is nicely marked. You can tell it was designed in the USA (I think). Someone on the marketing side must have insisted that the engineers make this device understandable to non-engineers or HVAC folks. 4) I also like the transparent cover so you can see what's burning on the board. That thing goes into the attic and if you check there it's probably because the heating/air conditioning is broken, which means it's very hot or very cold in there. Being able to see through without having to remove the cover is a good thing. However, the cover can be easily removed if necessary. 5) The setup/operational documentation provided was clear and well written. Thanks again to the marketing guys for proofreading and editing the engineer's speech. The only downside was my surprise that an external power supply was required. The block I replaced didn't need it. But this block is also out of order. Maybe because it didn't have an external power source. :)General. a good product!