"It would be nice if it could be taken all the way, though."
I am not sure what you mean with "all the way" as the new connect() options are fully compile time based.
One of the advantages of the now additional runtime checked option is that it does not require information on the concrete types of sender or receiver, while still keeping type-safety for signal/slot arguments.
"The other issue when integrating into a wider non-Qt project is that Qt-using code is no longer strictly C++: It's a Qt dialect which is processed into C++ at build time (I'm referring to the slots: syntax etc)."
No, this is handled by the compiler itself, or rather its preprocessor. A Qt file is a standard C++ header or source file, as can easily be verified by running a C++ compiler on it manually. Same is of course true for the file generated by moc.
It would have been an unmanagable situtation for Trolltech to deliver a custom compiler for all platforms they supported.