I can't believe that I just read through this whole thread. Here's a few things that came to mind.
Firstly, I never let herps wander unsupervised, and most of mine are temperate creatures that don't require high temps. It is just too big a risk. Yes, you can create a 'jungle room' with a fair bit of care and effort, but then what you are really doing is creating a very large custom enclosure, not letting the herp run free. Occasionally, I will put the blue-tongued skink or beardie on the floor while I clean their cage, and them put them back. That's about as far as I would go.
Other people listed a few of the problems associated with this, but I think only one mentioned a huge one- fire. There have been several cases of people having their houses burned down by free roaming herps (usually iguanas) that knocked over lamps, etc. This is one reason why insurance companies are not big on herps.
On the same note, another problem that insurance companies have is that people who create 'jungle rooms' (actually, even just regular herp rooms) don't usually create them to handle the high humidity for the long term. Walls rot, mould grows, and down the road it is a big cost for repair. If you still own the house, it might be your problem, but if you've moved (or if you were just renting) it will probably become an insurance claim.
For these reasons it is becoming difficult to get house insurance if you have a herp collection. Therefore they alone should be enough reason not to let your herps free roam if you care about the long term future of the hobby.
As for herp handling, I can't agree more that playing PS2 with your ball python around your neck is not a great idea. Nor walking around in the park, doing dishes, etc. However, I wouldn't agree that handling should be restricted to just when cleaning cages. Most people have these animals as 'pets', and assuming that they've chosen wisely (i.e. not a nile monitor) they can and should be able to handle them for 'fun' within reason.
Also, I have recently come to believe that captive snakes, especially, benefit from additional exercise beyond what they get in their enclosure. Size of the enclosure isn't relevant- the snakes sit in their hides most of the time, they don't need to move much to thermoregulate, they don't need to forage for their food, and they don't need to escape predators. Handling them is a poor substitute for these things but I believe that it is better than nothing.