just came on to see what latest advice was and real used how conflicting it is! I use one And plan on continuing for a while yet. my youngest daughter is now 11 months old and she's had two bumpers on her cot since 6 months old. She was getting feet through bars, turning them and not being able to pull them back, therefore getting herself really distressed!
My experience with my eldest three is that they never used them to climb out of the cot ... although I had one monkey lol who could climb out of anything anyway, and it was not unusual to come into his room when he was about 18-24 months to find him on top of his wardrobe! we never figured out how he got up there, but did excel at gymnastics (and sports generally) when he was older lol!
Tahira (mum of 33 yr old, 32 yr old, 30 yr old and 11 month old + 9 grand kids!!!)