Thanks for the review - very timely and interesting. In a nutshell, beyond the boot times, performance is close enough that if you move to MS 8, it's pretty much only because you prefer that UI.
Or, you know, you might be interested in the improvements to multi-monitor and printer support, File Explorer, Task Manager, backup and restore procedures, parental controls, and power efficiency or new things like Windows To Go, Storage Spaces, Hyper-V, IE10, native ISO/VHD support, less Windows Update-related restarts, improved accessibility features (namely Narrator), integrated malware protection, SkyDrive integration, UEFI support, WDDM/DXGI 1.2 and whatever else I'm missing. Now, I'm not saying everyone should upgrade because Windows 8 is the greatest thing since sliced bread, but let's not imply that there's nothing new except an ugly Start screen and better boot times.