Currently using them. Added 30 to the 540g about 6 weeks ago and they are still going strong. See 3-5 just about every night but definately see a reduction in anemones. We had a major infestion and are slowly seeing an improvement.
They are said to take quite a few months to actually take care of the problem so patience is a must. Have also heard that if you don't see them it doesn't mean they are not there.
For introduction, we added them at night, we shut all of the pumps off, and used a turkey baster to place them on the rocks and made sure they were able to take hold. We also set them in about 4 different areas of the tank so that we would have multiple colonies growing. Also need to make sure you don't set them on any anemones, they will get eaten.
So far they seem to be working but the test will be whether the anemones come back after the bergia are gone. That is the issue with peppermints, copperbands, etc as they never get them all or they are unable to get to the foot.