Just tried using 14.04 daily build (10th Dec) on HP Pavilion Touchsmart 11. (Aside note: This is the first build since 12.04 that actually runs on this PC - previous releases lock up with a black screen or terminal login prompt that doesn't run anything).
The installer starts, but does not detect that Windows 8.1 is already installed on the PC.
I was hoping to install 14.04 alongside Windows - I'll scrub Windows when the full LTS is released, but until then I need to keep it.
I did not proceed with the install as I wasn't confident that I'd mess up the partitioning and end up without an OS.
ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubiquity 2.17.0
ProcVersionSignature: Ubuntu 3.12.0-7.15-generic 3.12.4
Uname: Linux 3.12.0-7-generic x86_64
ApportVersion: 2.12.7-0ubuntu1
Architecture: amd64
CasperVersion: 1.336ubuntu1
CurrentDesktop: Unity
Date: Tue Dec 10 20:56:42 2013
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash --
LiveMediaBuild: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20131210)
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)
I can confirm the bug with Ubuntu 13.10 on a Dell Inspiron 3721.
It had Windows 8 pre-Installed, to which I had added Ubuntu 13.04 on a second partition. I had disabled UEFI and secure boot, because I hadn't managed to install Ubuntu with UEFI active back then.
When Windows was later updated to 8.1, the updater tacitly removed the grub bootloader, so I couldn't boot into Ubuntu any more. To fix that I chose to install 13.10 freshly.
The installer offered me to update 13.04, or to completely replace 13.04 or to do something else. Under 'something else' there was no mention of Windows IIRC. When I chose to completely replace Ubuntu, the HD was newly partitioned, so both the windows and Linux partitions were scrapped and replaced by one large partition that filled the entire HD (and a small swap partition).