Most irritating detail is the interaction where there is what looks like a select box (little down arrow and everything) but it expands when you hover over it after a small delay.  The delay ends up being the most irritating thing because it is just enough time for me to accidentally click where the drop down <i>used</i> to be and is now a home button!<p>It is small but this gets me every time and it is just such a gross usability fail.  Maybe this is unfair but I have a hard time getting past it to give g+ a chance when my first explorations smacks me with an experience that is so poorly constructed and violates so many obvious usability best practices.