Not sure if it still does this today, but Messenger Plus used to install adware by default, including a new browser search bar...I think Patchou removed this, but if not, be careful during install and uncheck the box that will include the sponsor program.
Messenger Plus has some nifty features, but it has been known to be a bit buggy and unstable. It's a hurry-up-and-ship program, and you need to be keenly aware of which exact build of Messenger you are using...every different build of Messenger requires a different build of Plus.
I've personally never used it. I would suggest hanging out at the forum at
mess.be or at
Neowin for more info. Mess.be also has a library of other add-ons for Messenger.