UPnP:
Here you go with the files after compiling, but you'll have to rename some files, because aMule expects Linux file names. Also I don't know where to put them.
I don't know what causes this delay in preferences, I've been looking at this code for the past days (On Windows, there'll be pointers to 0x01 created, which cause a crash on opening the prefs), but I can't find what's wrong.
Spellchecker: I guess that's standard on Mac OS X, please fill a bug report (bugs.amule.org) and I/someone will have a look at it later.
Look: Hey, we've got a new skin system! Create a nice Mac skin (take care of copyrights; help in the wiki) and it will look better already. Else, please specify the problems compared to other Mac apps for a Linux user with OpenBox.