I think as general rule of thumb, most people regard ISP supplied routers as being sub-par. I guess it depends how much people want to "tinker" with their setups. Most people just want out of the box PnP.
I have just been browsing the BT community forums and it does seem that the Smart Hub has issues, however nobody is going to post if they don't have issues.
True but you could say there might be loads of people having problems who dont use forums.
Thing is from HH3 they have improved quite dramatically upto the point of the HH5 where you really dont need another router unless you want to tinker. Wifi could have been better but it is a smart piece of kit. So when the HH6 came out it had higher expectations and at first it was brilliant. For me it went downhill with the June 2016 firmware release.
Only thing I am a bit narked about it is I'm a long term BT triallist and I missed out on the HH6 trial through being on holiday.
I even had an Asus AC68U for a bit but it doesnt play ball well with BT TV Internet channels on Ultra HD Boxes so went back to HH5.