See Harald Hoyer article: Fedora 17 Boot Optimization (from 15 to 2.5 seconds).
One of the boot steps that consumes about 3 seconds is the decompression and running of initrd. If you do not use LVM, software RAID or partition encryption you may not need initrd.
But Grub2 is configured to always use initrd for booting. If you modify by hand the file /etc/grub2.cfg, it will last until your next Kernel update. To avoid this, I made a grub configuration file that will generate entries without initrd even for new Kernels. Check it out at:
[peter@ace Fedora17-fastboot]$ systemd-analyze
Startup finished in 1433ms (kernel) + 2150ms (userspace) = 3584ms
3.5 seconds is good for me and I still have a fully operational Fedora 17. :-D