Holo was initially developed by someone at XDA for non-ICS phones to get somewhat of the ICS experience. I thought it was a nice launcher, very responsive, but lacked some of the customizations I was hoping for. On top of that, it didn't really give me the ICS experience I was expecting, so I didn't try it out for very long. One thing I definitely missed (compared to Go Launcher Ex) was being able to group all your apps in your app drawer into folders. I love being able to group all the apps in folders, in the app drawer, so it doesn't take up screen real-estate (more room for widgets of my most used apps) and I don't have to scroll through multiple apps, just to find that one app that I have that I use only every now and then. That function alone is one of the main reasons I'll be switching to NOVA.