I've worked for BT as both agency and directly over two years at more than one site in multiple different departments and roles.
The only thing I can say I loved most about BT are the people I worked with, but most people say that in their own jobs.
When joining BT: You will receive 2-4 weeks training dependent on your line of business and 6-8 weeks in 'grad bay' or 'consolidation' where you'll get good support and coaching from 'floor walkers' who are assistant advisers.
There after you'll still be constantly learning new things about the job and systems however there's nothing else to really aim toward unless you're loved by management and are to meet targets; in this case you'll be able consider progression to become a floor walker, cover manager and so on.
The only issue with "progression" at BT is that it's no guarantee unless you're a direct entrant manager or higher who generally have little experience in telecoms therefore are extremely useless. BT as a corporation don't seem to learn from this though so that'll never change. You can of course move sideways by transferring to different departments and roles however this novelty soon wears off once you've mastered your role and you get bored!
Advice: be likeable, easily manageable(not needy) and be adaptable to change otherwise you will not fit in and you will be 'performanced' out of the business which is what managers WILL do.
Rotas provided four weeks in-advance usually, salary
Management, flexibility, unrealistic targets, progression