What's the problem?
If UEFI is so great, why hadn't you heard about it until the recent fuss over Microsoft trying to use its secure boot feature to keep Linux off PCs? Ironically enough, one reason is that for a long time Microsoft didn't support UEFI. Even now, 32-bit Windows doesn't support booting from a UEFI system. Without Microsoft's full support, OEMs were reluctant to commit to UEFI.
In addition, UEFI is just a framework. If an OEM wants to offer full support for all the possible hardware that might be available on a given motherboard and offer diagnostic tools, it has to create them. That's not cheap. Apple, HP, and IBM have made the commitment, but other vendors have been biding their time.
A UEFI-based system doesn't require that its designer provide diagnostic tools and system controls in a GUI, but some OEMs, like Asus, are providing that kind of functionality.
Now that Microsoft is insisting that Windows 8 PCs must support UEFI-secure boot -- a sub-system designed to make sure that a PC only boots a legitimate operating system -- you can be sure almost all 2012/13 PCs will be using UEFI as at least a basic BIOS replacement.
Contrary to popular opinion, Linux developers have no problem with secure boot. Indeed, as The Linux Foundation white paper, Making UEFI Secure Boot Work With Open Platforms (PDF), states, "Linux and other open operating systems will be able to take advantage of secure boot if it is implemented properly in the hardware."
The key is that Microsoft continues to dodge the question of how they'll implement secure boot. Eventually, I suspect Microsoft will quietly back down from their "our way or the highway" approach to secure boot and you'll be able to both use secure boot and run any UEFI-compatible operating system you want on a Windows 8 approved PC.
That said, don't think that UEFI will turn out to be some kind of panacea for rootkits and other low-level malware. It's not.