Look, I'm not the type of person that install of kind of things on PC just for the sake of curiosity. However, this time...OK, I downloaded it, installed and checked out the features.
My conclusion after "playing" with it a little (I struggled to send/receive emails, at the end it works but I was expecting to be easier) is: I know is not good to argue a moderator (even when he's slightly wounding you) so I will stop discussing about Opera Mail features in a thread called "Gmail plugins".