The only glitch folks seem to have is in relation to the O2 sensor. Some people experience surging in the fuel injection. Most common fix is to remove it and run the bike without it. I've not had this, or any problem, with mine. And I've run it with 3 different exhaust configurations as well as with, and without, the O2 sensor. So it's not a problem for every bike. The topic has been covered fairly well here on the DML.
Other than that, which is specific to the 1000 motor, there haven't been any other problems people seem to have. The rest of the chasis and instrumentation are common to other Monster models and have seen wide use over the years. No other common problems have been mentioned with anything else.
Overall people give the bike rave reviews. Even the folks with the O2 glitch don't let it spoil their fun. It's a great bike.
I have mine for sale right now. It's listed in the Classifieds section. It's also on Ebay right now. Good luck with your shopping.