Three is joke, I think the three stands for poor service, poor customer service and poor me choosing them. I have wasted so much time talking to people in Indian call centres I could have written a Shakespearian play with a type-writer.

When you get an issue you call them and wait 20 minutes to be cut off, and then you call back and can't hear then. Remembering that you are calling a telecommunications company. then you get cut off again. finally you call then to say you want to leave.

When it works it is fast (60+Mbs)and good for streaming. The high latency seems to slow the whole experience down and does interfere with Now TV and occasionally Prime. Netflix is largely unaffected. Not good for gaming. Huawei ai cube needs a reset about once a week.I would go for the Huawei b525
Given up trying to sort router out with very poor customer support. Still better than the iffy slow fibre (speeds frequently below 10Mbs) I used to have

Dreadful customer service - I took them to the Ombudsman who upheld my complaint against them.

Quality of 4G data service is bad. Download speeds vary 0.5Mbps - 30Mbps with average probably around 6-12Mbps. However, there are widespread reports of Threes network traffic management causing 'stalling' when initally loading webpages. I've been experiencing this since Jan/Feb 2020 but Three continue to deny there is any issue and refuse to investigate fully. Using a reputable VPN service instantly alleviates the issue, proving the issue is with Threes network traffic management, but VPN services will a) cost money b) impact download/upload speeds.

Recently seems to have settled down. Occasional problems with streaming but this only once needed a reset. Speeds still 50+ Mb/sec average. Most problems seem to be with the Huawei cube and ethernet.
Still happy(ish). Better than open reach for me with no problems with multi users and speeds.

Only had this service for a few months. When it works the speed is good at about 60 Mbs. Over the last month the service has gone down on about 7 times. There have been well publicised problems with Three because of the signal tower upgrades. If this is sorted out and reliability improves I will be happy.
The customer service however is woeful. It takes ages to get through to someone who makes you go through the same process every time. Hours of lost time. Website seems stuck on "there are problems with the service". A bit more honesty and clarity needed.

works well when they are not arseing about with the masts, then it can be terrible. always get a payg sim and check it works where you need it to