Why Should I Keep My Kindle Fire?
This is not for the faint of heart since you can potentially brick your device and requires some technical skills to switch over. Also the custom ROM's are mostly beta level and are prone to bugs and instability.
If you are interested This is the ROM I am currently using:
I would recommend you take some precautions and install a root utility that allows you to make a backup of your current configuration in case something goes wrong:
You also will need to gain root access first to start your hacking journey:
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See my link above about gaining root access:
Rooting the KF will not give you ICS but it may be a happy middle ground for you if you want the best of both worlds.