Qt is a great library, better than wxWidgets in many ways IMHO. signals and slots doesn't is just the tip of the iceburg :3
also don't worry about the "stuff added on" it's VERY fast and moc does a heck of a job of translating everything before compile time. Yes the debug libraries are huge (QtGuid4.dll is > 100 MB) however the release runtimes are tiny offsetting this.
one tip i have is to RTFM, it's your holy bible of Qt, don't bother trying to remember anything, if your confused about something simply look it up. The documentation is extensive and covers almost everything (a few things are so simple it's not necessary to document them entirely)
My only gripe is the "custom" make file (the .pro) used by Qt Creator, it can be cumbersome and difficult to understand and is not documented well (yes I realize I just contradicted myself).