The patches enable all non-packed frame-buffer layouts to use ShadowFB acceleration and evdev is used rather than the broken KDrive keyboard driver. With Atari, 1/4/8 bpp modes now work while 2 bpp isn't yet supported. On Amiga, 1/4/8 bpp also work while 2/3/4/5/7 bpp modes are not yet supported and there's also some keyboard mapping issues.
Uytterhoeven says about his Xfbdev patches, "I haven't benchmarked it yet against XF68_FBDev 3.6, but it's unusable slow on my Amiga 4000/040, even for just moving the mouse pointer. May be due to excessive TLS syscalls with recent glibc. It is usable on ARAnyM on Intel Core 2 Quad."
For those interested in this Xfbdev support for vintage hardware, see the mailing list patches.