Well, Ubuntu 13.04 (Raring Ringtail) seems to run much better on a Macbook 5,1 (late 2008) and MacBook Pro 5,1 but it still has issues in that grub doesn't properly dual boot although the base install instructions work fine if you are completely replacing your Mac OS (but they don't say that in their main documents argh!!!).
But there There seems to be a big support team at Mactel Support Team. After two boots, the ReFIT I had on my MacBook Pro seems to work properly, but ReFind doesn't at all on the MacBook so it is mainly a problem with dual boot.
Looking (chasing) through all the documentation, I found that there is an alternative install that isn't on the main Ubuntu screen called 64-bit Mac (AMD64) (confusing since Mac's use the Intel chipset, but apparently this is really the 64 bit build) and there is a character interface install only for servers as well at Ubuntu Release 13.04
These issues have to do with the fact that the boot EFI that Mac's use isn't UEFI (alphabet soup right?). See Question #162838 : Questions : Mactel Support

In 10.10, I changed the standard amd64 images to dual-boot on either BIOS or UEFI systems (UEFI, "Unified Extensible Firmware Interface", is a different kind of firmware found on many newer systems). This was done using a technique known as a "multi-catalog" CD - it contains two boot images, and the specification says that the firmware is supposed to pick the one it can best use.
Unfortunately, even though Macs use a variant of EFI (an earlier version of what's now called UEFI), they apparently can't cope with multi-catalog CDs, and simply refuse to boot them (https://bugs.launchpad.net/bugs/633983). This left us in rather a quandary: we needed to support UEFI systems, but we didn't want to drop support for Macs either. I therefore created the amd64+mac CD images, which are exactly the same as the amd64 images except that they only support BIOS booting. Macs are happy to boot these in their BIOS emulation mode.

Question #162838 : Questions : Mactel Support

> Why are there no "32-bit Mac" images? (you need 64-bit images to support more than 64GB of main memory and for some graphics and compute intensive applications)

There's no need for them, because the i386 images still only support BIOS booting, and so the conflict with the Mac firmware doesn't arise. This is partly because very few people care about booting a 32-bit operating system on UEFI - and the UEFI people tell me that it's dubious whether that's even consistently supported - and partly to avoid this very problem.

Looksl like it might be an issue with the (of course) graphics driver although this refers to Ubuntu 11.10 not 13.04. See 11.10 - Installation Hangs on a Macbook Pro 5,1 - Ask Ubuntu

The "default" graphics driver in latest (K)Ubuntu live CD(& DVD)'s is Nouveau (more on the Nouveau wiki page). This driver does not function properly along with the Nvidia GT9600M graphic card. The problem is well described in Bugzilla Bug #27501, nVidia 9600M GT (Macbook Pro current model) is unable to boot.
One can workaround this show-stopper by pressing for example the F6 key (which is for to add/alter the kernel boot command line), then immediately press Esc and add nouveau.noaccel=1 as an extra instruction. Read more at X/Troubleshooting/Nouveau. Also valid are the instructions over at the respective wiki page for the Macbook Pro 5,1 and Ubuntu 11.04 Boot/GRUB/Plymouth.
This worked for me today using a Kubuntu 11.10 64-bit live DVD.