As some of you may know, 32-bit Windows XP users only see 2GB of memory no matter how much memory they have installed.
Windows 7 users see 3GB of memory IF they're running a 32-bit version and 4GB if they're running 64-bit -- as far as Fallen Enchantress is concerned (native 64-bit programs can see effectively unlimited amounts of memory).
The #1 thing holding us back on having "more" stuff is memory. We've been optimizing memory a lot in the past month so that we can stuff more but it sure would be nice to have even another 500 megs to play with.
If you are using Windows XP, I would really recommend upgrading to Windows 7 soon. FE will probably be the last game we make that supports XP.