They're kind of bad (there's always that other excuse: limit yourself) seeing how the majority users are hooked like a drug addict lately (crackberry is an example)
I don't know for tablets, I don't own one yet (Kindle e-ink doesn't count, does it?), but for smartphones I do not agree. They are tools. Powerful tools, like a Swiss army knife on crack.
They can be overused, and there is a full "phone politeness" to build, but it is not a reason to luditely dismiss them as useless toys.
Things my smartphone allow me to do:
- Get GPS turn-by-turn navigation from a link received in chat or direct search, including traffic info. (In China it is GPS is a near necessity)
- Find a nice mountain path when hiking around.
- Get an answer immediately when some wikipediable question arise in a discussion.
- Get translations from and to Chinese, English, French.
- Quickly prefill some new contact info and expand it on my computer later. Take a pic of the contact so I remember better how that is. (Helps with this Chinese names).
- Best: Build my own tailored Fuzzy Pinyin to English dictionary and push it to my phone, so I get a faster search. No dictionaries I know are that fast. Needed for catching up during meetings.
I won't say I never use it for games or news checking. It happens, mostly on the toilets, but it is not the main use.
Most people are using it for entertainment.