But on a good note, I figured out how to install Windows 10 on a GPT/UEFI enabled partition. It's actually quite simple. The reason why it installed it in legacy mode for me is because I used the Win7 Download Tool (which, strangely, doesn't download Win7 at all) to create my bootable Win10 USB drive. It formats the thumbdrive only as an MBR partition, which means it'll install Windows as the same.
To install Win10 (or Win8 if you so please) on an EFI device, you just have to use a utility that'll allow you to create your bootable ISO as a GPT partition. I actually did this entirely by accident while playing around with Unetbootin and Fedora 22. I saw that my thumbdrive had two entries on my boot drive selector. One labeled USB, and another UEFI. Selecting USB installs the OS "legacy", and UEFI allows you to do the obvious thing.
So I've learned something new. Kinda obvious in retrospect, but not very obvious in practice.
Also, when the official, honest to god RTM iso is released, I'll probably use
Rufus to create my USB drive.
The only downside is that I have to wipe all my partitions and install Win10 from scratch when I do this, but...eh, I was gonna do that anyway. Not looking forward to it, though.