Tablets - too bulky to be portable, too portable to be practical
I worked in an NHS trust IT projects department a couple of years ago, where we trialed a couple of different tablets (Panasonic prototype and MCA).
Nobody bothered to use them.
Largely it was the lack of suitable apps, which is really key for touchscreen devices - the windows menus are too fiddly, on-screen keyboard is too slow and takes up too much real estate, and handwriting recognition just didn't work well enough (not to mention the training and config required to get it working with a full medical dictionary for 20 different users). The panasonic tried to get around the shortcomings of stylus driven devices by implementing a resistive touchscreen as well, but it just wasn't accurate enough and we ended up turning it off as it was too frustrating (prototype device so maybe drivers got fixed for production).
Another major factor was the lack of sufficient hands - who knew that nurses are still only available with two arms each? Once you're carrying the device, you only have on hand free, so no pushing a trolley, or doing anything clinical without putting the device down. And they really weren't all that usable handheld - fine for short stints, but too heavy to use for a whole ward round. No, you need to put them down to use them effectively, by which time you may as well have a laptop (with keyboard).
Once the applications are available which are designed for touchscreen use, there will be a niche for tablets, but this isn't it. You will never get doctors using tablets because they just aren't portable enough. Docs need a device that can go in their pocket, or they just won't use it.
Despite all the naysayers, the iPhone is a pretty good platform for deployment to non-geek users, who just want to use their simple app for a quick and dirty task. It may not be great for "power users", but caters well for the lowest common denominator - and surely we can agree here that delivering effective medicine is the point, not delivering the be-all of smartphone devices? Battery life is a factor, but once you get into the realm of pretty UIs, processor intensive apps like imaging, 3G and wireless connectivity, battery life will diminish, regardless of vendor. None of these devices are designed for constant intensive use, as that is not how most are used in the real world. Anyone spending 5 hours using their phone as a portable computing device through the course of a day could probably have got that work done in 3 hours sitting at a desk in front of full-size PC.
"Medical grade" devices are IMO largely just an excuse for charging 1500 quid for a touchscreen PC with an Atom processor and 1Gb memory. Yes, it may be easier to clean, but that doesn't mean it will be cleaned while pens, hands, pagers, mobiles and shirtsleeves continue to spread bugs around.
I will always remember overhearing a nurse on a GI ward, on hearing of a ward closure due to C. Diff, opining "Oh no, I bet I'll be off with the runs tomorrow, I'm always the first to come down with it" - while chewing the end of her pen, sandwich on the desk in front of her at the nurses' station.