Connection:
Speeds of 60-90 mbps are typical in my area, on the coast, 5 miles from the nearest mast, across a large bay, with line of sight. I have the ZTE MF286R modem which supports LTE+ and I am impressed with the speed improvements over the year that I have had the service. In this area, the other networks have proved less resilient or predictable than EE. Price-wise 4GEE is on the slightly higher side but still relatively modest in comparison to other bills. I have unlimited (own router) for £25/mo on an 18 month contract.
Customer Service:
I have been very happy with the billing enquiry part of EE's customer service, which is very friendly, polite and efficient.
Technical support:
The only part of EE's mobile broadband service that I find disappointing is tech support. Like many others, I find the CG-NAT limitations on the EE network frustrating, but I understand there is a need to manage the limited IPv4 address pool carefully. I want to run a modest home server and access it remotely but I can't because CG-NAT addresses are not specific to one connection. The only other solution is an IPv6 address for my server but no-one in EE seems to know how to set this up.
I have solved this in a clunky way by setting up L2TP service with aaisp.net.