I find that AppCode tends to start at about .5GB of real mem use, expanding to about 1.2GB over a morning's work. This is with my current project, which is moderately complex (containing several related projects, static libs etc), but not huge (a couple of hundred classes).
This level of memory use seems on the high side to me -- by comparison, XCode 4 hovers around .5GB. But I haven't used a large java app before, so perhaps it's normal.
This isn't really a big problem -- even with my modestly-equipped (4GB) macbook, AppCode runs nicely. But am just interested in whether this is to be expected, or might reduce post beta.