I have the version that includes a fan and still had that happen. But it only happened once and it was on a hot Texas summer day, but then again I seldom use that cradle anyway. USB connectivity gets me everything except PlugIn and video playback (neither of which I care about) without the hassle of taking off my case -- though in either of those scenarios, I usually forget my phone in the car, so I pretty much stick to Bluetooth audio except for long trips.
All in all, ~$250 for a cradle that will almost certainly be incompatible with the next-generation iPhone is a pretty raw deal IMHO.