As an aside, why do we get a Tux icon, but no daemon?
While I only skimmed this quickly, it seems to be nothing new; just a better translation of the French sneak preview that surfaced a week or so back on ANN.
In any case, XFree86 (perhaps a misnomer; as far as I know, it's also used to provide X on PowerPC platforms, being the major free X11 project) 3.x.x does not support 3D accelleration directly. However, it *does* support the 2D accelleration features of various graphics chipsets, including the Matrox Gxxx line. In either case, the design of the X protocol itself means that graphics are most often mediated through the server, which itself must mediate access to graphics hardware through whatever *NIX-like kernel is at hand, meaning that graphics are rarely blazingly fast.
XFree86 4.x.x introduces GLX (a subset of OpenGL that can be propped up by Mesa, not unlike the Warp3D port for AmigaDE), and to obtain GL support at all, the server naturally runs in a direct-access mode (look up 'DRI' and 'DRM' on Google) similar to that previously only used through some odd hacks. I'm not sure if this really improves 2D performance at all, but it surely can't hurt.
Basically, XFree86 3.x.x should have "decent" 2D accelleration for supported chipsets, while XFree86 4.x.x has "excellent" support in some cases. When graphics are mediated through the *NIX equivalents of MUI, the libraries are often the sticking points (TK, GTK, Qt, whatever Gnome uses), and nothing but a faster CPU may help that overhead.
If someone's complaining of slow performance, it may be that certain things were constrained by the security model (I know I get only 15FPS under an older 2D music-visualization app that would fly under Windows and DirectX, using an 850MHz Athlon), or by libraries hitting the CPU (TK and GTK fly on my machine, but I won't touch anything Gnome-related), or finally, by poor 2D support for the graphics card used (I don't believe the Voodoo3 never saw fully open-source support, and thus, it's questionable if its drivers were fully optimized by people more familiar with X11 and XFree86's limitations).
Hope this sheds light on something. The currently single-user AmigaOS doesn't have security concerns with its graphics layer, and thus can use direct-access for just about anything; OS4 will be the same, and should show performance comparable to DirectX (but without the Windows overhead, and with the optimized code of current Amiga ports!)... It can also run the graphics drivers at highest priority, whereas XFree86 3.x.x may be limited to the amount of CPU the running user is allotted. (It does all vary on the way the particular distribution sets things up, but basically, 3.x.x would require much more tweaking than 4.x.x to get direct-access level performance.)
One final semantic note- It's not "X11 3.x.x;" X11 is the protocol, and is currently at revision 6, though I think XFree86 4.x.x may be extending it to X11R7. It's "XFree86 3.x.x," where XFree86 is one implementation of an X11R6-compliant server.
