I think Flowergirl summed up my understanding of induction.
I talked to some friends, did lots of reading on it and basically it would appear it is often more unpleasant as you don't have time to build up a pain tolerance to the early contractions as you tend to go straight in to the bigger ones. You also don't get the (usually) more gradual build up of dilation (esp in first babies), so your body has to deal with everything in one go. Hence people often finding it painful.
Also as has been mentioned, induction is more likely to lead to other medical intervention of some sort than if you go into labour naturally. Why this is is open for debate (and research). Some think its because induction usually causes more women to opt for strong pain relief (an epi) which can cause things to alter and therefore then might require forceps or some such etc.
There is also the debate as to if induction causes stress to the baby as its not actually ready to make an appearance. You are likely to be monitored when induced and therefore babys reactions can/will contribute toward what the Doctor does medically with regards to your labour. Of course if LO isn't ready its bound to change how they might react in labour when its brought on so quickly. This goes into possible medical intervention again then.
I personally am not in favour of it for myself unless there is a strong medical reason for it. Either the health of my baby or myself at risk. Otherwise I hope to go into labour naturally, even if it means I run 2 weeks past my 40. I have been asked to see my Consultant at 40+10 to discuss induction but I am hoping to be left to 40+14 if all is well. Every woman is different and what she chooses to do is totally her own choice. No one *has* to have an induction. Up to 42 weeks is considered within the time frame to go into labour naturally, but for some reason many hospitals don't wait till then but induce a fair few days sooner. Some women prefer to be induced rather than wait those extra days, some don't. Each to their own
Of course, I hope I don't need to make that appointment
Its interesting reading if you look in to it. Lots of reports, studies etc out there on it. I also discussed at length with my MW about it.