Haven't had any major problems with iOS7, Only small issue the animation takes a second or two longer than it used to, Apart from that it's fine, Plus now the folders are bigger so no need for so many 
Haven't been able to use airdrop only apple device I've got is the iPhone.
Haven't seen anything called in the car, Maybe only for newer cars 
So, as our Jobs crazed crApple fanatic. Should I upgrade from my perfectly stable and usable ios 6.1 to the buggy ios 7, and why?
I'm not gay, so "because it looks cool" isn't a valid reason. TBH, I think it looks crap anyway, but thats unimportant.
iPhone 4, 4S, 5 can only be upgraded to iOS7 though unless you've got another apple device ?
I'd say if you have a iPhone 5 yes upgrade to iOS7 but any other iPhone seen as I don't have another iPhone apart from the 5 I can't comment on how iOS7 affects the devices performance.
You failed to offer a reason why I should 
Something like this ?
The obvious, Fresh look like or hate it, Folders now hold loads of apps...
Handy quick access to a few features by swiping from the bottom of the screen upwards, AirPlane mode on/off, WiFi on/off, Bluetooth on/off, Do not disturb on/off, Portrait Orientation Lock on/off, Screen brightness adjustment, Music player, AirDrop, Flashlight, Alarm/Clock app, Calculator and Camera..
Siri has been refined and you can change the voice, Photo's app has been improved more organised, Mail app has been improved somewhat you can mark all as read and more I'd imagine have looked too much into it, Safari browser has been improved with a few handy features like I've mentioned in a previous post swiping from side to side to go back or forward, To close a tab just swipe and to look through just scroll through the open tabs, While browsing a page while scrolling down on portrait view unlike before all icons vanish and re-appear with a touch of any of the corners or if you scroll upwards..
I'm sure there are other reasons plus/negative points...
Personaly I like it OVERALL, Apart from the animation which slows things down a second or two..
