Although the files saved from TextEdit and Preview are actually saved in the cloud (and not just synced), they don't have corresponding iOS apps.
One of the biggest problems with iCloud is that an app can only access files in its container. There is no ability to open files from other apps. This is even more of a problem now that apps like Preview and TextEdit, which deal with generic files, are iCloud enabled.
If you are a developer, you can view all the files from all the apps stored in your iCloud account at developer.icloud.com. You can also download most of the files from there, but normal users are stuck.
So, if you only have one Mac (and any number of iOS devices), then the iCloud part of Preview and TextEdit is useless, other than that it provides another method of manually backing up a select number of files.