Cost of switching

I am certainly not the first to make this observation, nor will I be the last. Switching from something that works OK to something that works a bit better probably won't happen. Huge generalization, yes. But we are mostly lazy and if switching requires lots of effort, we won't do it.
What brought this home? I was given an iPad by my employer (well loaned actually). I already have a Motorola Xoom whose quirks I am finally used to.
The iPad is gorgeous. The screen is crystal clear, the rendering spot on, the speed of response to user actions is great, the battery life seems to be wonderful. So why haven't I switched?
There could be several reasons:

• Switching makes me admit I bought the wrong device
• Switching requires me to relearn the User Experience
• Switching means giving up some features in return for others
• Switching means giving yet another big brother some basic information about me
• Switching is work!

There isn't a single compelling reason to switch. Sure if I had not bought the Xoom, and was just starting the tablet journey, I might well buy the iPad. But having a device already means that I have to overcome some inertia. How much inertia? In this case a lot. The Xoom does pretty much what I want, so I am getting little more valuable functionality in response to the cost (of my time) that I put into the switching. While the iPad is an emotional purchase, it hasn't stimulated my emotions enough to want to part with the Xoom.

That and while I thought the Xoom soft keyboard was poor, the iPad one is hideous by comparison. Shift keys for each number? And we are told to have letters and numbers in passwords. It's too bloody difficult

Human "Technology"

I have been bothered for a while by the calories in/calories out model of weight thinking. I have finally articulated at least to myself why I have difficulties:

• My scale doesn't weigh "calories" it is all about mass.
• Energy seems to be a proxy for weight (and no I am not in the e=mc^^2 realm of thinking because that deals at entirely the wrong level!)
• The energy in/energy out doesn't account for a few things (which I will detail out in the body of this posting)

So, here's the fundamental set of thinking. Please comment and point out the holes.

Taking the assumption that I am interested in what the scales say, I should be thinking in terms of the total inputs/outputs. Even without understanding any digestive processes.

Weight at any point in time = weight at previous point in time + weight of all inputs since that time  - weight of all outputs since that time.

It's the all inputs/all outputs that we need to worry about.

At the simplest level the inputs consist of:

• All solids (food)
• All liquids (drink)
• All gases (air breathed in, water vapor in the air, etc.)
• Supplements

At the simplest level the outputs consist of:

• All solid (fecal) material 
• All liquid (urine) material including dissolved solids
• Vomit
• Sweat
• Respiration products (gases, especially Nitrogen and Carbon Dioxide, but total of all gases)
• Water vapor in respiration products
• Anything else we can think of (dead cells, sputum, tears, ear wax....)

It's no wonder we use energy as a proxy!

Now for the area where I have trouble with energy in/energy out. There is a move afoot to extract energy from human waste. That must mean that there is some residual energy in some of our outputs. Especially, I suspect in our feces. But maybe elsewhere too.  So the big questions for me are:

• How much of the available energy is in our waste products?
• Does the amount of available energy in our waste depend on our eating habits? If so how?
• Does the amount of available energy in our waste depend on any conditions (eg Celiac disease) we have? If so how much effect?

Any thoughts/comments gratefully received.

Chris