I've been using CCleaner for a long time and have a few suggestions:
The context menu for the items on the registry tab has 'Deselect All of Type' and 'Deselect All' listed even though the list is deselected already (visa versa too).
This should depend on the current state of the list. List items could be disabled (grayed out) or not listed depending on the context.
The ability to "add to ignore list" would be great. Maybe a button in the bottom right "Ignore selected issues...".
It would be great if CCleaner could backup the whole registry and also be able to optimize (compress and defragment) the registry.
These are standard features found in other similar basic cleaner and registry tools.