It's interesting to read threads like this and form a strong belief that something will either be good or bad based on what the majority says, but we should be wary of anecdotal evidence found on forums online. Everyone has a different experience and you won't get a clear view of an issue by reading responses. Then again, by looking up the studies in journals you might have trouble deciphering the good studies from the bad as well.
Back when I was about 20 wks pg I was wondering the same things about epidurals, and I looked up the studies. It quickly became clear that like others have already said, there wasn't a clear causation between the epidural and further intervention, or whether it was a correlation due to the need for an epidural being indicative of a more difficult labour. The studies do agree that on average, the epidural does lengthen the second stage by about 15 minutes. They don't show a consistent difference in length of first stage labour, though. And it is true that women with epidurals are slightly more likely to require further intervention like assisted delivery and CS (this is where the question of correlation vs causation sommes into play).
And with the newer low dose infusion epidurals that are used the NHS suggests that women should be able to adopt positions to assist the process, such as kneeling or side-lying. By far there is more evidence to suggest that bad positioning while in childbirth leads to further intervention. How many women with epidurals are told to lie flat on their backs so legs up in stirrups? Unfortunately most still are, despite being perfectly able to adopt a position that might make it easier for baby to descend.
At the abysmal NHS antenatal class in my area I asked about this and was told that if I felt capable of kneeling on the bed I would be more than welcome to, but that they would never suggest it on their own in the first place. This is even with my trust telling us the epidurals they offer are 'mobile' and patient controlled.
I'm a first time mother and I'm confident that if when I go into hospital I feel I won't be able to cep with the pain, I am happy to ask for an epidural. I will not be having gas and air due to previous experience with it, and do not want pethidine. I know the epidural means having a drip and a catheter as well, but I don't mind. I'll have control over how much I top up the epidural and can decide to stop when it gets to second stage to allow for the return of sensation.
All in all, for me the epidural seems the best choice for pain relief during labour should I need it. If my hospital would not allow me to adopt various positions in labour or if the epi wasn't low dose and patient controlled I might have a different opinion so I think it's important to find out from your hospital what their policy is.