[nickel3956]

I am about to get a Galaxy Nexus and wanted to trade in my Epic with Sprint's Buyback program. My Epic is running CM9 and I was wondering if they wouldn't accept my phone unless it was on stock.

[ratsttam]

They will accept it as long as it's working. But I would still install the stock image via ODIN and not bother powering it back up afterwards.
My reasoning: It'll be 100% stock, with no chance of your personal information being on the device. Backup then format, or outright remove the SD card to further protect your info.

[iviyth0s]

I agree, they don't really care about rooting anymore but the secure erase aspect of it will give you piece of mind