I've been using GalnetMiui for a few months ever since the early beta days up until one of their most recent Chameleon RC2 release before switching over to MiuiAndroid. My understanding is that Galnet's team tries to improve the official Miui rom with features and functions of their own, but since Miui is a closed source they were restricted. They have recently implemented their own framework which is great but with it comes teething problems and stability issues.
I've grown tired of flashing their new release only to re-flash back to an earlier (more stable) version. Great effort on their behalf but for someone who is just after a stable, clean rom with good battery life on all future updates I think official Miui is the best way to go. This is why I have switched from Galnet to MiuiAndroid rom.