I have. Expect long, start, stop labour, slow (I mean incredibly slow) progression and dilation a and severe pain in your back.
What I would say is having now been through it you can:
Rest as much as possible between contractions (sleep even if just snippets) because you may be in for the long haul. Also eat in the early stages because you will need energy (you won't feel like it but just nibble). Stay in water if it helps.
I don't know what your opinions on pain relief are but with my back to back I was adamant I wanted nothing...Ahhh how I changed my mind with the back pain. Gas and air helped hugely and then an epidural to relax me and help baby turn.
It's hard but totally doable. The worst for me was expecting it all to happen quickly and to keep being told I hadn't 'progressed'
Is it your first baby btw? I think second babies would be quicker.
It's really really good your midwife has identified it as being back to back, they will help you along and support you. Mine didn't realise until I was a long way in and so I struggled without the pain relief. A big sign for me was no or v little pain In my tummy and severe pain at the base of my back.
Good luck, it's sooooo worth it in the end!!