The Nokia 5800 was the first Symbian S60 v5 based phone from the Finnish giant. Nokia was heavily criticized for the clunky and out-dated S60 v5 UI. However, the 5800 sold like hot cakes all over the world, and still does, thanks to its irresistible price and features like Free Walk and Drive navigation. Due to its popularity, the handset is also very popular among the modding/developer community. Custom firmwares for the 5800 were out for quite some time now.
However, the folks behind PNHT have now managed to port the Nokia C6 firmware over to the 5800. Except for a few differences including the side slide-out QWERTY keyboard on the C6, the internals of both the phones like Processor speed, RAM are totally identical. Users who are interested in installing the Nokia C6 firmware on their phone can check this thread over at PNHT forums.
The Nokia C6 firmware is also compatible with the Nokia 5530. Kudos to the folks at PNHT for their hard work!