Actually I was wrong, IvyDE is already pushing errors in the problems view just like Maven does (I should better know the software I maintain ! ).
I think I still let the errors popup because sometime the error message can be quite long and to manage readability, the carriage return are inserted.
See for instance:
Error while resolving the ivy instance for ivy.xml[runtime, test, compile] in 'cas':
The ivy settings file 'file:/Users/hibou/dev/svn/tools/build/ivysettings.xml' could not be parsed: failed to load settings from file:/Users/hibou/dev/svn/tools/build/ivysettings.xml: The element type "ivysettinssgs" must be terminated by the matching end-tag "</ivysettinssgs>".
And this is not readable in the problems view... It would be not much better if everything was on one line. Maybe we can hook something on the double click on the Ivy problem ?
And another case which should be taken care: in the launch configuration we can reference ivy files on the file system which is not part of the workspace, so the problem view cannot be used for reporting that kind of errors. Here a popup should still be mandatory, but a dedicated one would probably be better than the default error one, for sure.