Isn't comparable to the mobile app in terms of features. Doesn't sync tree notes automatically, doesn't have a functioning timer, doesn't have a 5 minute rest period, doesn't show all trees planted(only in the browser session) Doesn't save if you exit the browser without syncing. And many many more.

Edit: Now with the recent update, notifications no longer work, so you don't know if the timer has ended.

Edit 2: Now sync doesn't work. USELESS, might as well set a Google timer since it core functionality works better then this extension as of now.