I have known a couple of folks who did a 4 layer board at home
How did they do that? 4 single-sided PCB's layered on top of each other? I usually try to squeeze out a single-sided PCB when I'm designing one, double-sided works too. Not that Ive designed a lot of PSB's though.
Ive never used geda, maybe I should try that too sometime but Im kinda sold on kicad. One of the things I like about it is that you are not locked to a particular footprint for any component. Kicad have 4 main parts, EEshcema for schematics, CVpcb to assign schematics to footprints (or "modules" as kicad insists on calling it), PCBnew PCB editor and a a gerber viewer.
Of course you must have the pin names corresponding to each other (schematics to modules/footprints) for a correct PCB layout. If the parts dont have that, its not that difficult to make your own parts. (But Im kinda skeptic about making my own library with lots of parts in it, as I seem to be good at overwriting those with a new one, with the lates part only... or something like that. Its a little while since I used it now, but although Ive used it a little while theres still things I havent got used to yet. Library administration is one of them).
But anyway its a really nice electronics cad imho, but certainly also quirky. Id be pretty lost without some guides, like this one: http://www.curiousinventor.com/guides/kicad
Another thing I like is that it is cross-platform, linux and windows. I dont think its for mac though. And no size limitation (apart from an A4? but you can link several together). There is also a lot of libraries (many converted from Eagle too) for it.
Oh, and a nice addition is the 3D viewer, to visualize the board while you make it. You can even make your own 3D models if you want, with the wings3D package.