I have the 720 SW of that range.
I've literally kicked the crap out of it... and it's great. It is very very robust.... so the crush-proof and freeze-proof one must be amazing!
Sandy beaches. Bouncing RIBSs. Filthy floodwater. It's done it all with me.
Video quality is good, but not exceptional.... but it's a photo camera... if you want video, buy a video camera! Sound quality is poor.
The underwater snapshot mode works very well (the other two underwater modes are only if it's in the underwater diving housing)
I'd strongly recommend this kit with it:
Particularly the bungee cord with the carabiner. I clip it to my PFD, wherever and I've no worries... it's very strong. I once handed the camera to someone to hold, and ran off (forgetting it was clipped to me) the cable stretched about 4 metres, so it's no problem with the weight of the camera.
Also very useful for clipping to my belt when I'm out on the piss... then I never lose it!
The software that comes with it is pretty good.
I did look at the Pentax before I bought this one, and I have a friend who has it. I would agree that it's not as solidly built, but I don't think there is really a lot to choose between them.
Hope that helps.