We have had one for the mindees for 5 years, and just about to replace it as it is well and truly bounced out, (we did look at getting replacement pads and buffers for it, but it cost more than replacing the whole thing) we have a net, couldnt get CM insurance without it.
Touch wood, (going to jinx it now arnt I) we have never had a accident, but we do have very strict rulews, that they are only allowed to land on feet or bums, no flips, and one at a time for the older ones, The toddlers go on together with supervision, but they just tend to run round it!