If you enter a \ in gpk-application's search text area although the 'Find' button disables you can still hot 'Enter' and get an error dialog.
1) Disallow entry of unaccepted characters. I'm not sure what the HIG says but I think it would be nicer to simply disallow \ as a valid character or filter out those characters before a search
2) Disable enter on that entry at the same time as you disable the 'Find' button
I don't think we should just ignore characters -- then we get angry users thinking their keyboard has a fault. I also don't think we should just ignore the <enter> when there is invalid text -- then we get bugs about "certain search works being ignored".
Yes hard call, which I guess is your call ;)