I've been using the C-7 for around 2 years now and I bought the C-8 as soon as I saw it available. Primarily my reason was the external antenna. My Z Wave network of 45 devices had around 30 connected directly to the C-7. I had purchased the various bits to fit an external high gain antenna on the C-7 as detailed on the Hubitat forum by Lewis H; however, I never went ahead with the modification as I decided my eyesight/soldering skills weren't up to the task. There was a minor hiccup during the migration process. My issue was that unless you had a Hub Protect subscription in place, the free cloud backup that takes place during migration was not visible on completion (even though it was successful). I reported this on the forum and the HE team have now amended this to avoid confusion. Once migrated the Z Wave routes get cleared from the database, so although everything worked straight away, it was a few days before all of the routes and neighbours populated in the database. I'm now seeing 40/41 of 45 devices connecting directly so there's a definite improvement in Z Wave coverage with the external antenna. There have been teething issues with Zigbee inclusion, as the C-8 uses a new Zigbee chipset over the C-7; however, these bugs seem to be about resolved now after several firmware updates. My only ongoing issue is that 500 series devices that support S0 (but not S2 security) cannot be added with security set at 'none' to the C-8 (or C-7) - at least not without the use of a secondary controller and Z Wave Controller software. This is an issue caused by SiLabs SDK and there's nothing Hubitat can do to resolve it. It's frustrating as we have so few 700 series devices available in the EU/UK frequency of 868 Mhz.