about using designer or qt creator instead of writing all the gui design directly on c++:

Not having used glade when i started to write rapier (because i was not sure how easy glade would be to use with hildon thingy at the time) was something i regretted afterward.

Having a way to handle change in the gui with a 'what you see is what you get' tool makes enhancement and changes much more easier. Especially if you are not familiar with the application in the first place.

Rigth now, i know i would not like to have to add another something in the Rapier preference windows by example, and this sort of change could (and should) be really simple to do with a graphical designer.