The new version of Avast upgraded seemingly flawless on my computer (Win7 Pro SP1 & CRP), but I found an issue with the restore settings dialog:
When opening a .avastconfig-file created with Avast 17, the following dialog window doesn't show me components to select/deselect. Choosing Continue does not apply the saved settings.
This doesn't happen when selecting a .avastconfig-file created with a prior version of Avast.
As a workaround, I can open such an old file, click Abort, and then select a file created with Avast 17 (without closing the UI window in between) to get the dialog working properly.