I stopped at 24 weeks - I worked as a Barista in a cafe over summer, which was complete chaos and all staff members fell apart at the end of January and slept for 2 days solid, we were all so exhausted... as soon as I stopped, the leg, feet and back pain stopped. My physiotherapist would have killed me if I hadn't stopped about then... some of the advice suggests standing on your feet for 5/6 hours at a time from 26-28 weeks onwards is not such a great idea, but it depends on the individual - if you're feeling good and physycally able to cope with all the standing and heavy lifting aspects of your job, then you're free to make the decision on other considersations, like how prepared you are with getting the nursery ready and whether you need to consolidate bedrooms and so on. My GP was doing 12 hour shifts as a registrar when pregnant with her first child at 36 weeks, as was several other doctors at the time, and they all got pre-eclampsia...eeek.
I'm 27 weeks and am quite happy pottering through my daily chores, and I can just lie down when the heat of the day gets too much (rather than trying to keep working and not being physically sick in the process). I could not work as hard or fast or lift full crates of milk and crockery as i would be required to. The pro side of stopping early is, according to sleep-deprived friends with 6 week-old newborns, is that you get a bit of a rest in whilst it's still possible to rest. And you get some more time to finish that baby knitting! The cons are: financially it is not a lot of fun (I'm sewing cot sheets out of old flannelette sheets at the moment and we are living from one pay packet to the next), and there is the danger of becoming socially isolated when not working... hence why one should hook up with your local playgroup mornings BEFORE the baby arrives so you get a bit of support from new mums!