OK; it's almost three years later, and Linux Mint, XFCE, and Mac4Lin have all progressed, each one growing ever-closer to "perfection".
The "original" Mac4Lin is outdated -- doesn't seem to be anything happening on the project website, other than reader comments -- the last (v1.0) version was released mid-November 2009. A "fork" -- by the folks at Make Tech Easier -- was been released in June 2010: Turn Your Ubuntu Lucid to Mac OS X
(although the title references "Lucid", it works beautifully on my Linux Mint Debian Edition, Xfce edition, v201204).
Speaking of "my" installation, it's worth noting that it's a virtual one, running in VMplayer/3.1.5 with 512MB RAM allocated, and the underlying hardware is a dual 1.4GHz PIII CPU with 2GB RAM, running Linux Mint 11, Gnome edition.
And the LMDE/Xfce duo do work fast... and smoothly. That is, once Flash-heavy websites are closed in multiple-tabs on Firefox -- what a resource hog! Closing two pages (both mainstream, commercial newspaper sites) brought the load down to a workable 1.40, from a much higher 3.03.Next step:
Installing LMDE/Xfce w/Mac4Lin on my Asus EeePC 1005PEB, which sports an Intel Atom N450 @1.6GHz and 2GB RAM.