I intentionally sought a new machine that supported UEFI, because I wanted to play with some of the awesome stuff it makes possible, like loading a firmware module to export the hard drive contents over iSCSI/NBD/whatever.
So far I've had nothing but good experiences. I turned off legacy boot in BIOS and am booting both Fedora 17 and Windows 7 with UEFI boot. It's great; they don't fight over the boot sector anymore, as they have their own separate UEFI boot partitions. Boot is faster. The "BIOS" setup interface is way less awful than anything I've ever used before. There are no volume size problems to worry about thanks to the GPT.
Don't lose sight of the fact that regular BIOSes are awful in all sorts of ways too. At least with UEFI the vendor can fix them without needing to get their bios-assembly-code magicians out of their padded room.
I'm not saying UEFI won't present problems - it does. Just that those problems are not all new or unique.
This particular issue has cropped up repeatedly in ACPI tables, to the point where Linux now just reports its self as Windows to ACPI to stop manufacturers doing idiotic things like this.