Since I didn't know about it, I'll assume that few people do. :)
If you've installed F10 rawhide and are seeing a grubby scroll bar instead of the promised pretty boot, that means your video card is not supported by plymouth (i.e. it's not ATI). If you really want to see the "pretty boot," you can instruct the kernel to boot in vesafb mode by passing a vga=*blah* parameter on the kernel line.
For the values of *blah* you will need to refer to this 8-year-old document. E.g. on my laptop, with a 1024x768 max resolution, I boot with "vga=0x318".
Keep in mind that vesafb is "old hat" -- the resolutions it supports are quite limited. For example, there is no easy way to set a resolution of "1680x1050" because it's not a regular 5:4 ratio display. This is the reason why F10 is sticking to cards/drivers that support "modesetting" -- which is currently limited to ATI (or "most ATI"). Using vesafb is a workaround that may or may not work for you, if you care enough to try it.
Though, honestly, if you're not seeing the "full glory" of plymouth boot, then you're not missing much anyway. ;)