Sorry I feel a bit like an idiot asking this... but if my C5 is running fine at the moment and I have no plans to add anything new in the near future, are there any advantages to upgrading to the C8?
I know the specs of the c8 vs c5 but I am curious if I will see any actual performance difference or additional features....
The processor and RAM are the same, so "performance" in that sense should be similar; as you may be aware, the biggest differences are Z-Wave (much bigger difference between the C-5 and C-7, but also a slight upgrade between the C-7 and C-8) and Zigbee (from the C-7 to C-8; C-7 and earlier are mostly the same, aside from external radios you may find on older models). If you notice improvements, it may be from any of a few things:
Other changes you might be aware of:
Those will probably not have much of an effect on your daily use.
Personally, I have a lot of Z-Wave devices and find the Z-Wave changes since C-5 worth it, but I can't say whether you would. 
There are certainly a few new features, though, especially with Z-Wave, beyond just the hardware changes.
If everything is running fine I’d highly recommend not “upgrading”. I did and regret it. Nothing but issues with my zibgee devices. Went from having a working setup to having to constantly fix things. Just stay put. Why risk it.
My C5 was working great but I just figured it was time. Had a few initial glitches with the C8 but got past that and now all is great again. There is more info on Zigbee and Zwave on the C8 and that can be a hindrance as I now see things that concern me. Probably had same thing on C5 just didn’t know it. But everything is working just fine so I ignore it.
I agree with this. If I had it to do over again, knowing what I know now, I would not have done it. I'd give them some time to figure out what is going wrong with ZigBee and get it fixed first.
What's concerning you?
I probably didn't state that very well. Apparently there is more info available on the C8 for the Zigbee and Zwave details that wasn't available on the C5, or if it was I didn't know it. For instance I had a ghost Zwave that I wasn't aware of before.
None of that is a problem, just my mind sometimes thinks less info is better.
To address the original intent of this thread. The only problem I had with the migration was cloud access after a router reboot. But that was solved fairly quickly. I know a lot of people have had all kinds of issues, but not in my case. Everything is humming along nicely.
Well a ghost is problematic and should be removed ASAP as it can cause issues in your mesh even if you don't think so.
Agreed, but when I wasn’t aware of it…. 
So now that I am, I’ve had to order a stick as I can’t get seem to get rid of it otherwise.
If you can figure out the device that cause it, power down the device, then power cycle the c8 for 2 mins and bring it back up. Then attempt to remove the ghost.
I would also point out that just because some folks had a ruff go of upgrading not all did. I got a C8 immediately after launch and have not had any issues with it. That said most of my devices are Zwave and not Zigbee. I have not had any issue with the 17 Zigbee devices I have though so
As I understand it the Zigbee issues are real, but there are two sides to this. One of them are users that are using devices that are already problematic like Aqura devices seem to have even more issues with the C8. I think if you already have Zigbee devices you had to do special things for to get working you may have more issues with the C8 and it's improved radios. The second group is just some devices seem to really have a problem staying connected to the hub. I haven't experienced this myself but there are enough posts on the forums and notes in change logs that this is clear. What I am not clear of though is how many people fall into each of those categories.
I would strongly caution you if you already had to tweak your setup for touchy zigbee devices about upgrading to a C8. If you have just raw reception problems with devices though like my KOF Zigbee fan controller that seems to be working better.
Regardless of anything else though the old saying "If it isn't broke don't fix it" can certainly apply here.
Many folks have migrated without issues. I am not one of them. For me it's been weeks and weeks of frustration. But everyone's risk tolerance is different. If you feel you need the advantages of the C8 and understand the risks, go for it. Otherwise... hold off.
Have you checked your ZigBee stack
http://hubs.ip.address.here/hub/currentZigbeeStack
For a C-8, it should say "Hub is set to use new Zigbee stack." If not, use this endpoint to switch it over:
http://hubs.ip.address.here/hub/useNewZigbeeStack/true
For a C-7, it should say "Hub is set to use standard Zigbee stack." If not, use this endpoint to switch it over:
http://hubs.ip.address.here/hub/useNewZigbeeStack/false
Yes
What's this about a new zigbee stack? I just updated from C5->C8 recently and have had a lot of problems with Hue Outdoor motion sensors. In fact I just put my old C5 back in service just for 2 of them, which are now attached to it and appear on the other hubs via hub mesh. Hopefully they stay connected -- too soon to tell.
But I just saw this, and yes my new C8 is responding "standard Zigbee stack" But I can find no information anywhere about this or how the "new Zigbee stack" is any different/better?
On another question: is there somewhere a doc about all these secret URLs and what they tell me and what they mean?
No docs. Just what we have that's been provided by the dev folks.
You should definitely use the URL to update to the new Zigbee stack.
Curious about this new Zigbee stack. Mine says Standard. Should it be switched? I'm not having any Zigbee issues.
Yes. Although, I'm not exactly sure what it does as that's beyond a level of insight we usually have. I presume it has something to do with hardware support for the 3.0 chip in the C8 vs 1.2 in the C7.
It might be but i also saw where this was discussed for a version 2.2.3 back in Sept of 22. That clearly pre dates the C-8 release. That is a beta release though. It is also already turned on for my Dev hub which is still a C-7
My C-8 is still running the standard stack as well, and I am not seeing any issues. I would really like it if we can get a link to where we are told to use the new one instead with the actual differences. Anything i can find on this seems very vague and unclear.
You won't see big differences after upgrade.
I upgraded from C5 just to have newer hardware and Zigbee 3.0 radio.
I think now it is safier to upgrade (current firmware 2.3.5.117) but begining was terrible. I was just a step from downgrading to C5 because a lot of problems with Zigbee network.
Now everything works fine. All my Aqara devices, no matter if connected directly or through Sonoff ZBMini, are paired and work as expected with no problems at all.
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