I installed rEFIt, then made a USB stick with unetbootin. It boots into a live system just fine, and it installed just fine (apparently). The system boots into rEFIt, then I select Linux and it gives me a GRUB screen.
During boot, however, I get some errors. The boot experience is different each time.
Every boot results in strange graphical issues. I will either not see the Ubuntu loading splash at all, or I will see it in ugly text briefly before it get prettier, but smaller and in the upper left quadrant, and then it disappears entirely (leaving a purple background) to make way for some terminal output, including letting me know that system v failed.
Some boots skip the Ubuntu splash entirely and leave me with a black background with some terminal text output. The most recent boot says:
ieee80211 phy0: wl_ops_bss_info_changed: qos enabled: false (implement)
ieee80211 phy0: brcmsmac: wl_ops_bss_info_changed: associated
ieee80211 phy0: wl_ops_bss_info_changed: arp filtering : enabled true, count 0 (implement)
ieee80211 phy0: wl_ops_bss_info_changed: arp filtering : enabled true, count 1 (implement)
mountall: Plymouth command failed
mountall: Disconnected from Plymouth