Since they have pretty much opened the gates I'm sure it is a little taxing on the resources I don't care how big you are. It's not just Google + but new Gmail accounts, people importing their FaceBook friends, posting what ever they can think of, there is allot going on I'm sure.
Just think for a minute how much is going on right now with Google + If on a normal day 48 hours of video is being uploaded to YouTube every minute. Just to try and put things into perspective.
It's got to be a major job trying to control the flow into this new social community.