I've had it for just over 3 months and the outdoor hardware itself has been flawless and super accurate in everything it records.
The wireless Observer-IP box inside my home did a great job updating Weather Underground but the Meteobridge connection to the Observer-IP would flake out every few days and start reporting odd data to all my services until I rebooted it. I troubleshooted it a bunch but ended up springing for Meteostick which is a USB stick that plugs into the Meteobridge and then the Meteobridge no longer needs the Observer-IP box, it can receive the signal directly from the outdoor hardware. This eliminated that problem.
With this setup it has been near perfect, although about once a month it will report a single (not repeated) odd data point (and remember it is sending data every 5 seconds) to my services OTHER than Weather Underground (perhaps Weather Underground automatically ignores a temperature of 1000 degrees or something, or perhaps the problem is with the other services like PWSWeather.com and CWOP) but on the very next update it is back to normal.
All in all I am very happy and it is very "hands off" at this point.