Although, its still alpha it did install painlessly. The procedure is:
1. Downloaded new rom. (.zip) to your SD card
2. Go to 'backup and restore ' and take a backup
3. Reset userdata, cache and dalvik !important
4. Install the zip from SD card
5. Reboot system and you are done
After the install if you already rooted your Cherry Mobile Magnum, it stays rooted. After the reboot, you'll notice that it doesn't have any apps. So get GAPPS and install it following the same procedure for the ROM.
Unfortunately the ROM, doesn't have support for the camera and WIFI yet. Edowar and team are still working on it. And they as nice as the ICS rom is to look at, they don't have an ETA.
Despite of the shortcomings, my preview of the ICS rom has had me convinced that to wait for a release. From what I can see, the ROM is pretty stable (1 reboot for the week I had it) and is choke full of eye candy.