Circles is awesome. I can't believe Facebook hasn't done it yet. Hopefully you can drop friends into more than one circle.
As far as Huddle goes, I hope it's easy to go from a normal text straight into a Huddle. Also, typing status is very helpful in a chat room to avoid the inevitable conflicts that occur when people happen to type responses at the same time.
Sparks looks somewhat like Google News filtering. I'm not sure if I'll use it if that's all it ends up being.
Hangouts could be interesting, but because it's many-many communication like Huddle, the conversation flow could be difficult to maintain. I hope it works out.
Based on the demo you can only put friends in one circle, but I hope that's going to change or just isn't properly reflected in the demo; I have plenty of people I would consider to be in multiple circles. The easiest example of which is a "co-worker" who is also a "friend".
Oddly enough, I hope this maps to the gmail groups concept, since I already have people mapping along those lines in there, and winds into my android device as well.
Google seems to run into the large corporation octopus issue where knowing what the left and right hands are doing is a difficult task.
I'm sure you can put people in more than one circle. Mostly because huddle seems to be based off of circles. While not being able to put people into multiple circles would be inconvenient, not being able to put people into multiple "huddles" would just break the whole feature for most people.
As far as Huddle goes, I hope it's easy to go from a normal text straight into a Huddle. Also, typing status is very helpful in a chat room to avoid the inevitable conflicts that occur when people happen to type responses at the same time.
Sparks looks somewhat like Google News filtering. I'm not sure if I'll use it if that's all it ends up being.
Hangouts could be interesting, but because it's many-many communication like Huddle, the conversation flow could be difficult to maintain. I hope it works out.