...I just have not found anything that has inspired me to change....
3 interesting devices - would probably be able to use any of them if HAD to: but not a one that screams "BUY me"...
Sliders tend to be thick, and top row of keys can be difficult to hit - and Fitaly is a faster input method than any tiny keyboard in the first place.
Treo should be thinner - but at expense of reduced keyboard size and screen: screen is doubtless great for a phone - but if its A Phone, why bother with a QWERTY keyboard in the first place? And the "S4" screen (Cute abbrev, btw!) is nearly useless for screen-based input and is second-rate even simply for reading data.
Not to mention that most pda/phone combos are thick (breath and/or depth), clumsy to hold as phones, & stuffed with non-productive battery-sucking features that run the price tags up, are 2nd class in terms of function, and likely to leave you high-and-dry (out of power) if you do use them....
JMHO, of course! (or: the contrarian point of view....

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