I actually have had two of these from Amazon.
After reading reviews about the lower priced versions of the Bosu I selected the pro version to make sure it would not break. When it arrived I read the instructions saying to inflate it to 30cms when upside down. I dutifully did this, used it for a bit then went to bed.
The next day I was shocked to see the ball had broken out of its frame and looking like a half inflated Swiss ball! Contacted Bosu in the States who said to get Amazon to replace (which they did with no hassle), and received the next one in the mail.
Was absoluetely rigorous in inflating it according to the instructions again (by using a ruler measuring from ground to the frame when the Bosu is upside down) then realised what I had done wrong first time around. When inflating the Bosu had tipped over slightly (after all it is balancing on its tip) and I was previously measuring the lower side - Duohh!
Anyway it has been perfect ever since (and I subsequently found out that with this model I could have simply reinserted the Bosu into its frame on the first one anyway - the cheaper model is glued so can't do this once the glue goes).
Anyway - don ensure carefully, don't over inflate and you'll be fine.