rEFIt's primary purpose is as a boot manager -- it enables you to select which OS to run. As such, it has little or no utility on a Mac that runs nothing but Linux.
That said, your configuration is likely to have some sub-optimal aspects:
- Chances are you've got a hybrid MBR setup. This is unnecessary in a Linux-only configuration, and since hybrid MBRs are flaky and trouble-prone, it's probably best to convert it to a straight-GPT or straight-MBR configuration. (Which works best depends on how you're booting -- use a straight-GPT setup for EFI booting and straight-MBR for BIOS booting.) You can use gdisk to either convert the hybrid MBR to a plain GPT setup or convert to a true MBR configuration.
- Completely removing OS X means you won't be able to update your firmware, and adjusting boot loader options can be tricky. OTOH, note that if you keep OS X, you may need to keep that ugly hybrid MBR, depending on your model's capabilities.
If you convert to a plain MBR setup, rEFIt is likely to stop working. (I've never done this on a Mac, though, so I'm not 100% sure how it reacts. I have heard of people running with such configurations, though.) In such a setup, you can treat the Mac as being pretty much like a normal BIOS-based computer.
Converting to a straight-GPT setup means that the Apple's BIOS compatibility layer won't load, so you'll need to boot Linux in EFI mode. Chances are you don't now have an EFI boot loader for Linux installed, so you'll need to do some reconfiguration if you go this route. I've written a Web page on this topic, so consult it if you're interested. If you go this route, you'll probably want to replace rEFIt with rEFInd and a 3.3.0 or later kernel with EFI stub loader support, GRUB, or some other Linux EFI boot loader.
Edit/addition:
To see whether you've got a GPT, MBR, or hybrid MBR disk, install gdisk and then use it to view your partition table, as in:
$ sudo gdisk -l /dev/sda
Password:
GPT fdisk (gdisk) version 0.8.5
Partition table scan:
MBR: protective
BSD: not present
APM: not present
GPT: present
Of interest here are the MBR and GPT lines in the Partition table scan area. If you see MBR: protective and GPT: present (as in this example), it's a plain GPT disk. If it reads MBR: hybrid and GPT: present, you've got a hybrid MBR. If it reads MBR: MBR only and GPT: not present, then it's a conventional MBR disk.
Alternatively, you can view the disk with Linux's fdisk. If you see nothing but a single type-0xEE partition, it's a plain GPT disk. If you see such a partition and other partitions, it's a hybrid MBR disk. If you see one or more partitions but none of them are of type 0xEE, then it's a plain MBR disk.
