I was with Three for years. It started off great, but the data throughput got worse and worse, and the prices went up every year.
I wanted EE without paying for EE, and I'm now with 1p Mobile for about a year and it's been perfect.
I've read that the only way to get 'actual' EE is to sign up for an EE contract then hope that you can beat them down on a retention deal when you're out of contract.