Well, the installer is just a 3-click process and can't be made simpler. It will just copy all the files to a mounted partition and assume you have set that correctly for your system.
What's a bit messy is creating said partition and making sure it can boot. We could make this a 3 click process too, but it would be a "wipe the hard disk and setup everything the way we want". However, most people would then complain that their precious windows/linux/OSX/whatever install was erased with all the data on it.
So, we went for something a bit more manual, which allows a wide range of solutions and will get you a running system only if you do things right. It also tries to be non-intrusive and not prevent you from booting other systems.
What this means:
- It does not replace the disk MBR, and assumes what you have there is suitable for booting (that is, a standard MBR that will boot the active partition). If this is not the case, you need "writembr" to install a suitable one. Alternatively, you can install bootman, which will add a boot menu (or GRUB, or another boot manager).
- You need to remember to mark the Haiku partition active, otherwise the MBR will not boot it.
- You need to remember to create your BFS volume inside a partition, and not as the whole disk (which is also possible, and used to be required on some devices, but people keep changing their mind about that).
So, the installer could warn in case the partition is not active. It could offer to install bootman if it detects some other OSes on the disk. But, I don't think making it automatically replace the MBR and do the partition layout is a good idea, because that means erasing data from previously installed OSes, which is not so nice (it is the Windows way, however).