I'm new to Android.
Wikipedia was my friend in understanding Android versions. I concluded that it's not usual to upgrade Android so the version supplied on your phone when you buy it is pretty much what you've got till you buy a new one. Win95 and Win7 were both pretty good and stable except many easy to use features have been expunged over the intervening period. Running Win7 on a 95 capable computer is asking for unhappiness and vice versa likewise. Here is my limited experience so far:
Samsung galaxy mini 2 GT-6500D 800MHz 3 1/4"
Gingerbread 2.3.6
Uses: phone, texting, GPS navigation, music, WiFi hotspot
Satisfaction: 110%
Samsung Galaxy Note 2 GT-N7105 1.6GHz 5 1/2" s pen
Jellybean 4.1.2
Uses: handwritten notes, read online and kindle reference books and pdf scientific papers, photographs, read MS office files, USB transfer to desktop computers.
Satisfaction 80%
Problems: awkward USB access, insufficient privacy, Firefox performs poorly (Chrome goes great but I would rather not), flakey external SD card
Unexpectedly good: handwriting recognition, reading office docs, very quick smooth touch performance, 3G hotspot speed 13MBps (twice what I get by copper line)
They're different tools. GB is very efficient on a hardworking telephone. JB can do the job of a desktop OS if you have the real estate.
I'll update but, seeing everyone's experiences here, will be upversioning as little as possible - not broke.