My major gripe with Emacs has been how it performs on non-*nix platforms. It seems kind of slow and bloated on Win, for example. Maybe it's just bad luck, but that's how it is for me. I also haven't ever seen any kind of Projects support in Emacs... but I'd be thrilled if someone pointed me to docs for such.

I can't really speak with much authority one way or the other with regards to the speed of Emacs on win32. I use Emacs minimally on Windows XP under VMWare (Mostly to keep my .emacs working in both win32 and Unix), and it seems to run quite well there.

I don't use projects myself, but oliverp pointed out Emacs Development Environment. I have not tried using it, so I don't know how well it fits your requirements.

I am a very big fan of the Speedbar. Since I began using the Speedbar, I've pretty much stopped using folding. It pops up a nice little frame with a list of files and folders. If you drill down into a file that it understands (like a perl script) it will show you a list of all your subs so you can jump to them with just a click. I don't tend to mouse much unless I am not sure of the name of the function I am looking for, and for that purpose this works very well.

The Emacs Wiki is a very good place to find out just about anything you ever wanted Emacs (and probably lots of stuff you really don't ever want to know :p).

Oknow

I've used emacs a lot on Windows (2000), Linux and Mac OS X. I've never really noticed any problems with any of the implementations. I've used CVS for version control in Windows emacs. I haven't noticed any speed problems with the Win32 emacs. I've also used the cygwin emacs port (with X), which is quite good but doesn't copy & paste between normal windows programs I don't think (if memory serves) and isn't as fast (the X implementation is quite slow). If I have to use a computer for any length of time (regardless of OS) emacs is one of the first things I install on it. Can't get far without a real editor.

For MacOS X I'm using the X11 emacs from fink, though I had to recompile it to get X11 support (not sure if that's still the case). Since then I've also installed the Carbon emacs port on other machines, which seems pretty good, though I don't like the default font.

(on a side note, now that I'm used to emacs keybindings (ctrl-a, ctrl-f etc) I really appreciate the fact that they work in many MacOS X programs (anything Cocoa). I find it frustrating when I use programs that don't have these bindings now)