I had one, 20 hours into what would be a 26 hour labour.
Before the epidural, I had laboured on gas and air, and was still only 3cam dilated. DS was having oxygen issues so I was immobile anyway (constant internal monitoring) - so having the epidural made no difference to me being able to keep mobile etc.
It wasn't because of the pain, it was because of the exhaustion. I had had false contractions the night before labour started, so hadn't slept in what felt like forever. And my birth plan (all that keeping mobile, being in the water) had gone out of the window with the monitoring.
The epidural was good - I got it in a timely manner, it didn't hurt and neither did the catheter. However, the tube did slip and as a result I had a patch of pain on the left-hand side, which was really annoying. They couldn't fix that, apparently. But in the end it was useful, because it meant I could feel the contractions to push! And a patch of pain was much better than what I'd had previously. I managed to sleep, rest, and 6 hours later was 10cm dilated without realising it 
I did have ventouse, but that was because of baby's breathing difficulties and the need to get him out fast, rather than the epi. And I walked out of the hospital 6 hours after DS' birth, feeling great. I would definitely have an epi again.
If you're not sure what you want: take the birth plan with you but keep it hidden until you see how things go. Have a chat with the MW/consultant BEFORE you get to the panicked stage - it's much more difficult to ignore a woman who is clearly compos mentis, than someone screaming in agony.