Extended downtimes for an app store are definitely not good for obvious reasons. The odd hour or two might be put down to something being switched over, but 12 hours is a no-no and doesn't exactly deliver much confidence in Microsoft's abilities to keep servers going in what they hope will be a bigger and bigger ecosystem.
Interestingly, the Store for Windows Phone 8.1 devices is fine. Obviously, the Windows 10 (Mobile) client is different and uses different architectures to populate its pages.
Can anyone help shed light on what's gone so badly wrong? Is it E3 and Xbox-related? Or is it that a major server centre has a catastrophic issue?
The Store was down as I went to bed at 10pm UK time last night and it's still down as I write this at 10.30am the following day.