Every Android device has its own ROM. ROMs are modified by the phone's manufacturer or others (like CyanogenMod). For Example, when I wanted to install CyanogenMod designed for Galaxy S (GT-I9000) on my father's Galaxy S Plus (GT-I9001), I have done a search since it is not designed for it. I have found that Audio, Camera and some other things will not work.
Every Android device gets its ROM released at a time different from another. I just can't wait to the ICS to reach my tablet.
Yes. I feel that it is more stable. Also the usable RAM (out of 1GB) was increased from 775MB to 830MB. It is much more responsive than 3.2 Honeycomb. It is said to have an option to disable apps. I will google about it to see if it is present in mine.
Edit: Disable apps successfully
Steps:
1. Go to settings
2. In the settings menu click on Applications
3. Select All in the tabs at the top of the screen.
4. Click your desired app and click on disable.
Note: doing this may be dangerous if you dont know what are you doing.
If you mean about rooting, I use AdAway, Chainfire3D (not working in ICS so removed it ), Cerberus, cant remember the rest.
Update: was playing around with system files and damaged Wi-Fi, forced to flash the ROM again (Factory reset wont work because it only restores settings to default and deletes all stored data).