The official milestone builds and nightlies are all VAC++. Never install Mozilla by overwriting an earlier installation. You're only asking for trouble. The only other basic rule is to keep the directory structure inside the zip intact. If there's no bin, you don't have to create one; you can just unzip into /warpzilla or whatever (assuming you don't want the binaries sitting in a partition root directory).
Nightlies are a crap shoot. The best approach is probably to install the latest one alongside a previous release, keep it if it's better or scrap it if it's worse, and repeat that process with each download. Bugs come and go from day to day (even hour to hour) depending on what code gets checked in and its effects. You basically get the tree in whatever state it's in at the time of the build. Milestone builds are a safer bet because normally three to ten days of branch stabilization and bug fixing goes into them before release. That's the main difference between them and nightlies. Otherwise both are complete packages. The plc4 crash apparently stems from not having Times New Roman MT 30 (the Unicode font) installed, and changing all references to it in the prefs files to Tms Roman (or something like that, see the relevant thread for exact details) has been reported to work. Theoretically, installing the font should also work. The readme from a milestone release generally holds true for the nightlies until the next milestone release and readme. The nightlies are an automated build-and-zip process, and don't include the readme presumably because it's not in the tree. There's also an implicit assumption that people who download nightlies know what they're doing. h~
