I made the switch recently upon getting my new phone. It works so smoothly with my desktop outlook and the WP8 system, that I am glad I made the switch. I had no real problem with the functionality of gmail, but I hated how hard it was to sync calendar and contacts between my desktop outlook and my android phone. In addition, Google's privacy issues had me very concerned. I did set up my gmail to forward to my outlook and I continue to use it for blog and podcast feeds which get sent to my phone via the next gen reader app. I would prefer to subscribe to them via outlook.com which would allow me to ditch gmail completely down the road, but I haven't found a good solution yet for that.
Bottom line, the switch is not really hard at all. You can even set up outlook.com to import your contacts and calendar from gmail.com, which makes it easier still.