Speedrabbit and Zeife have released kernels for our phones, as well as another user here and at SDX, Joey. The kernels will update many of the drivers of the phone, including display, camera, keypad, wifi, power, flash memory and more. You can get a lot more information on kernels
here.
Calkulin's ROM has tweaks in it, some stock apps removed, a theme added for desktop, icons, etc, as well as more stuff I undoubtedly don't know about. With his ROM you still need a kernel, so you can choose from those of Speedrabbit or Zeife.
I hope this helps.
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