Upgrading to 4.7 breaks old projects. Stick with 4.5?

I just upgraded to Flash Builder 4.7 and found that many of my projects are now broken. Many of my projects require a previous overlay of the AIR SDK and that doesn't seem possible with 4.7. For those projects should I stick with 4.5?

For the projects where I don't need to overlay an older AIR SDK, I see some of the following warnings:

The definition mx.core.ByteArrayAsset...could not be found

The definition mx.core.FontAsset ...could not be found

The definition mx.core.MovieClipAsset ...could not be found

The definition mx.utils.Base64Encoder ...could not be found

I checked my code and these "definitions" don't seem to be explicitly mentioned. What the heck did they do with 4.7?!

Should I skip 4.7 and stay with 4.5?