Problems:

1. Bootup delay (20-30 sec)

SOLUTION:

Insert OSX disc, boot from it, open terminal and enter following:

bless –device /dev/disk0s2 –setBoot –legacy –verbose

where /dev/disk0s2 is the partition you installed grub (do ‘diskutil list’ to find out correct partition). Of course, ‘–verbose’ is optional. This makes Macbook EFI firmware boot your Linux installation in legacy mode without long delay (20s vs 3s).

url: http://regebro.wordpress.com/2008/11/16/installing-linux-on-a-macbook-without-os-x/

2. Not booting into Linux
No bootable device — insert boot disk and press any key

SOLUTION:
boot from linux instalation cd in rescue mode
Install gptsync
Execute

gptsync /dev/sda