I've now had two back labours and they were very different - my son was back to back and the labour was absolutely fine - they did try to get him to turn during labour though by manoevering me around so I guess that may have worked, but I was in active labour by then and more than 5cm (was 5cm on admission with him) and it was still very manageable.
With Amelie I was induced early due to pre-eclampsia, but was still able to move around - I presume this was because I didn't have syntocyn or anything similar, just the tablet pessary the night before and then waters broken - she was also posterior and this time the pain was incredibly intense, far far worse than with my son, but the labour was very quick (in active labour for about 1 hour 20 mins before she was born!). The speed I suspect was due to the pre-eclampsia as pre-e labours are often hard and fast but the pain in my back was a whole new ball game. She must have turned at some point late on though as she was born the right way round, having been posterior for the past 10 days!
So yep, my experience is that it can go either way - be very manageable or not so much. But even with Amelie, I was just waiting for an epidural, so if she hadn't come so quickly the pain wouldn't have lasted much longer anyway, so there are options. I didn't want an epi ideally and was quite scared of the idea in principle, but the reality when I was there was that I was desperate for one so there is always that option! But you do cope, either way - I just had gas and air and tried to visualise the contractions bringing the baby nearer, and stayed upright to try to help the pain xx