Core M is a dealbreaker for me - same performance in geek bench as an iPad air 2 - right? (Hopefully I'm wrong with that stat)
iMHO the new Dell XPS 13 looks very tempting. 13 inch retina display in a 11 inch chassis. Al casing. 13 hour battery life. Large glass trackpad. Free upgrade to windows 10. Plus windows seems to play nicer with my network and nas set-up. I'll give it a few months but Apple really have to step up with the existing air line. If they come out with something similar with the new air 13 I'll be all over it, otherwise I could well switch.
Keep in mind that those PCs don't exactly meet the cooling needs that Intel demonstrated with their reference core m tablet way back in early 2014. The cinebench 11.5 score on that tablets is 2.65 which is on par with the mid 2014 MBA per notebookcheck website. Stupid ultracrapbooks/OEM windoze crap tablets making the core m far slower than what it can actually do. Just research about the Intel reference tablets on the internet and you'll see they don't throttle under extended benchmarks such as geekbench and cinebench