Matter of fact, I'm getting to the point that instead of a 'pure cell', instead I want a relative monster that I can use like a PDA/Ebook reader/MP3 player. No need to hold it to my head to make phone calls, I'll use a headset. Heck, make the the headset clip to the thing when not in use. BIIIIIG battery and long antenna.
I had one of those.
Big, thick PDA-thing running Windows Mobile. I had 4GB of flash storage on it for MP3's and software... installed some map software on it and bluetoothed it to my handheld GPS unit. Used a bluetooth earpiece for most phone calls.
Drawbacks:
1. It was a touch screen. So, if you didn't lock the screen it did all sorts of random crap. Extraneous phone calls, internet browsing, you name it. If you DID lock the screen, the hot-button on your bluetooth earpiece didn't work (because screen lock freezes all input into the device). Very annoying.
2. It was a touch screen. No tactile feedback on the number pad.
3. It was a touch screen. If the backlight gets turned off (see lack of screen lock above) then you have to go somewhere VERY dark to be able to read the screen to turn it back on... and you can't see your number pad if you need to make a call (see #2).
4. It was a touch screen. Very fragile. It's broken now, and I am carrying my 4 year old Nokia 6000.