I don't think you'll be locked in at all. Given that iCloud is already a web-facing service which you can use from a browser I can imagine we'll see clients for

I don't think you'll be locked in at all. Given that iCloud is already a web-facing service which you can use from a browser I can imagine we'll see clients for windows and possibly even android: Apple will want people in the cloud because ultimately it's a win for them. (They'll no doubt boost marketshare as well as "mind" share in porportion to the success of iCloud.)