Comment 4 for bug 811485

I recommend that the ESP's size exceed 200 MiB. The reason is that some boot loaders, such as ELILO, effectively require kernels to reside on the ESP. There's also a patch to effectively make the Linux kernel its own EFI boot loader, which would also require the kernel to reside on the ESP. If kernels go on the ESP, then the ESP's size requirements become similar to those for a separate /boot partition. An Ubuntu kernel and initial RAM disk together consume about 20 MiB, and I've seen them much bigger than this, so even a 100 MiB might not hold many kernels. (Fedora creates 500 MiB /boot partitions, as a point of comparison.)

I realize that Ubuntu uses GRUB 2 and so does not need to place kernels on the ESP; however, individual users might decide to ditch GRUB 2 in favor of ELILO or even the experimental kernel patches, and users might dual-boot with a distribution that does use ELILO, such as OpenSUSE. Note that Ubuntu includes an ELILO package in its repositories, so it's a logical boot loader for an Ubuntu user to try if GRUB 2 gives problems.