All very effortless and secure. Just give them third party access to your Calendar account (I don't need to remind anyone to not use their Google account password when signing up to NuevaSync) configure your iPhone to add a new Exchange account, select calendar synching, and away you go. Of course the only problem is if you are already synching with your work Exchange account you have to ditch that account first. But that's okay; just one less reason for me to check my work email out of hours :-)
Now I don't know what their business model is, how they intend to monetise this, or how long they will be around for - I just know its completely free right now, totally reliable (for the brief amount of time I've been using them), and solves one of the last jigsaw pieces in my never ending quest for 'Synching Shangri-La'.