I completed my MBA in 2000, studying part-time with the Open University Business School. I chose them on two key criteria: (i) accreditation - AMBA being the key one - and, (ii) the ability to tailor the degree towards my specialisms - in my case, finance. The organisation, study cohort and quality of the course was outstanding.
I did it not for the corporate ladder thing, but to enter an industry for which I was only partially qualified. At the time I was working iin a 10 person outfit and even now, in another organisation, there are only 11 of us - so its not all big corp. The learning is applicable across all corporate endeavors, large and small. There were, interestingly, a number of NHS staff on the course I did, and not just NHS managers, but senior nurses and medics too.
For me it was life and career changing (I had to study the hard way, having not been able to go to uni for a first degree) and I was extraordinarily lucky to have been sponsored by my employers.