Really good or overrated?
Really good. Trust me, I do not like British comedy, nor do I like American comedy (okay maybe Adam Sandler movies are funny for one time viewing), The Office is actually great. One of the few TV series I've watched but I have completed it years ago and I still prefer to rewatch some episodes rather than venture for new TV series. That's saying something.
Also, ignore majority of season 8 and 9. Like all good TV shows, The Office hit its low at a certain point, but the good thing is that they were aware and ended it in season 9 rather than milking it for 5 more seasons.