I had an ECV for DS at 37 weeks. I dsicussed it with my DH and my Dad (ex obstetrician, who I trust deeply) and was givena good run down of the risk benefit profile by the midwife who confirmed the breech. I was sent home to pack a bag 'in case of complications' and was very definitely told that at the slightest hint of foetal distress I would be whipped to theatre for an emergency section.
I was also given a good run down on likely success. For me, as it was my second child, not that far on in the pregnancy (at 37 as opposed to 40 wks) and that his head wasn't actually in my pelvis, jsut resting above it, I stood a good chance of a succesful ECV (in answer to a question up-thread it stands for extra-cephalic version).
In the end was pretty painless, I felt extremely well looked after and it was successful. It seemed their biggest concern was asking if I knew what sex he was as the screen was full of very boy looking bits! I was monitored continously for a good 2-3 hours afterwards before they were happy to let me home.
The little bugger then turned back, but turned again himself at 39 weeks and stayed put for another 3.5 weeks...
But- this is all anecdotal evidence, as are the extrememly sad instances where it goes wrong, much better to base your decision on the evidence form systematic review linked up thread.
Personally, I felt in my own situation, the risks were small, the chance of succes high and I desperately wanted to avoid a section so I could get my mobility and strength abck as soon as possible after a long pregnancy plagued with SPD.
Good luck!