The good things about maemo:
-awesome multi tasking still even after all this time...
-customise nearly every aspect of the device easily...
-organic app creation process, lots of user feedback and input...
-behaves more like a computer then a phone...
-the forum its organised compared to others, more like a community...

The bad things about maemo:
-occasional heavy lag makes you want to smash it into bits...
-lack of major developer apps...
-usb port failure, yes it does exist...
-its not fully open source and nokia lied about certain things...
-internal error closing application...
-crappy battery life and the phone get warm/ lol good for british cold winters...

The good thing about android:
-loads of apps, actively supported...
-high end hardware devices...
-might just take over the world lol its nearly in everthing...

The bad thing about android:
-runs poorly on mid to low hardware, really its that bad anything else is better...
-aweful multi tasking, makes you want to scream WTF...
-kindah junkiee market place as, in its hard to find new fresh good apps...
-poor battery standard one day use...
-force close and more lag...

The good thing about ios:
-very smooth nearly all the time...
-large selection of shiney polished apps...
-simple to use, no brain required...

The bad thing about ios:
-limited customisabilty even with cydia...
-useless paper weight without jailbreak...
-sorry excuse for multi tasking...
-no file manager...
-very poor call quality...
-but the worst thing is FREAKKIN GOD DAMN ITUNES... lol

btw i have used all of these os and end of the day its really up to you, use whatever makes you happy, even if its two paper cups tied to a really long piece of string... :P