I learned of a new problem with some Hewlett Packard desktops : an incompatibility with newer graphics card on not so old models (with Intel Sandy Bridge) and no BIOS upgrade to fix the bug.
That, and no way to lower the RAM speed on those OEM PCs to keep the PC stable when the RAM, motherboard or memory controller aged not too well.
On the other hand I've had some trouble with assembled hardware, software related, for doing dual boot or multiboot.. I have the bug of Windows-7-on-multiboot-fails-to-install-SP1 on my old BIOS based machine, and the friend's machine on UEFI gives me headaches : used to be that Windows 7 refuses to install (ha!) but I'm having trouble with grub2 seemingly failing to update itself (?) or stubborn on keeping the same configuration, so the dual boot to two linuxes still defaults to the "wrong" linux and the other linux doesn't use the new kernel I've installed.
So, due to the transition to UEFI you still can suffer crap even if you stay away from OEM PC.