I'm running pygame-1.9.2_pre20120101-r2 on Gentoo with SDL_VIDEOBACKEND=directfb, where directfb is using the hardware accelerated fbdev system on a raspberry pi.
Upon loading a png image with transparency, I can blit it to the screen surface without a hitch -- transparency is fine.
If I smoothscale the image I lose all transparency -- the transparent pixels are white on blit. convert_alpha() on the image gives a blank surface.
The same code works fine using the software renderer, i.e. on the X server on the pi and even other hardware.
Some framebuffer details:
/boot/config.txt contains: framebuffer_depth=32 framebuffer_ignore_alpha=1 framebuffer_swap=1 (necessary for colors to work right on directfb)
/etc/directfbrc contains: system=fbdev pixelformat=RGB32
fbset -s gives: rgba 8/16,8/8,8/0,8/24