I have to say that I'm absolutely LOVING MIUI (miuiandroid.com/) on my Nexus One. It's a really slick interface where I just haven't had to download and install replacements components such as dialers and contact managers (even browsers) because it all works together so well. It's a very productive ROM, and looks so slick too.
Android 4.0 - Ice Cream Sandwich has now been announced and the one of the key features is the unification (finally) of the interface. I.e. the way the device works should be far more consistent than it ever was before. Though this isn't exactly hard. Android has always felt quite segregated in the past.
I'm looking forward to getting my hands on the Android 4.0 and seeing if the move away from MIUI is going to leave me home sick. Watch this space!