I think one of the main reasons why Google+ is doing so well is that they have taken time to produce a really well designed user interface. Facebook's UI is really poor in comparison. As a user, interaction should come natural and with Google+ it does. This is highlighted by positive interaction from 'non-techy' users. It is actually a pleasure to use. I could happily create and delete circles all day long :)
there was a number of forecasts and predictions for some sort of lite interface that was to be crossbreeding of twitter and facebook UIs, in some shape.
This one might just be the winner. Time will tell... or maybe it will just find a niche and rest of the world will quickly move on.
