Although they say it is a "one time password" which is smart, email is still assumed to be not secure. Like for example, you wouldn't want to send your SSN through email because servers along the way can possibly sniff it. So, while it seems safe in most situations to do this, I feel that it probably isn't 100% safe but maybe good enough for most people.
What is the risk though? If someone did steal your one time link and get into the app could you somehow prevent them from continuing to access it? And what could they do in the app -- change your address and buy stuff on your credit card and send it to themselves? Feels like there is just some tiny level of risk here that probably wouldn't happen... but I wouldn't feel completely safe with this.
I still have no use for the full screen (Metro) start menu and apps since I use Windows 8.1 on a desktop and laptop. Classic start shell and running everything in desktop windowed mode is still all I need. I often wonder if I will someday actually want a Windows tablet instead of Android that would make this full screen stuff necessary. Until then, the full screen stuff is just annoying and ignored.
BizSpark is a great program and we were excited to take advantage of free Azure hosting included with it. However we learned from our customers that there is just too much latency between the web server and SQL Azure. We found much improved performance by moving to a Storm SSD server with the web server on the same box as the database server. Very happy with that decision.
A year or two ago I would have sided with the dominance that the iPad exerts in the market and felt that Microsoft was doomed without a tablet available until Fall 2012, but honestly -- I'm about to switch from my iPhone to Android and purchase a Galaxy Note II as soon as I can get my hands on it and frankly I've got a Mac and several Windows PCs and I still prefer the clusterfuck that is Windows 8 over OS X. Interestingly I think Microsoft still has a chance.