Re: question 1: iOS scrivener is not buggy. It is, however, infrequently updated, and therefore likely will not use the latest iOS bells and whistles. If this would bug the heck out of you, don’t buy.
Re: question 2: Many, many people (including myself) sync with never a problem.
That said, sync does not happen in the background in iOS Scrivener. While you can automate it to some degree, you will need to be consciously aware of sync. Most particularly:
- Don’t leave a project open on your iOS device—always navigate back to the projects screen, and sync if needed, before switching to your Mac.
- When switching devices, always leave enough time—in both directions—for Mac Dropbox to sync all your changes before modifying your project on either Mac or iOS.
If you believe that developing these habits would be difficult for you, then iOS Scrivener may not be for you.
Finally, not everyone shares @Login’s opinion that iOS Scrivener is superior to Mac Scrivener. I myself have largely abandoned iOS Scrivener because I find its limited feature set (compared to Mac Scrivener) frustrating. (Check this thread Features on Scrivener iOS: Equal to Mac? for a detailed discussion.) The last time I used iOS Scrivener was when I sent my Macbook Air 2015 to Apple for a battery replacement. It was an adequate substitute for a week, but it was a relief when my rejuvenated Mac returned.