And, our questions are (partially) answered. Shape Services (the makers of IM+) made a statement today on their facebook page:
Hi everyone, 
just a few quick announcements:
1) Push feature is now temporarily disabled, sorry for that. We will enable it within 24 hours. No application update will be needed.
2) Windows Live Messenger (formerly known as MSN) service support has been removed due to Microsoft Marketplace request. Hopefully, we will be able to add it back some time soon.
We appreciate your interest in beta round.
Please send us all your comments and suggestions.
Daniel mentioned in his video that push notifications weren't working, and now we know why! The servers are turned off. Also, the folks at Shape verified that Microsoft asked them to remove WLM support. Not terribly surprising, but it's nice to know we were right on both cur questions are (partially) answered. Shape Services (the makers of IM+) made a statement today on their facebook page:

Our questions are partially answered. Shape Services, the makers of IM+ (see video review), posted the following on their facebook page:

Hi everyone, just a few quick announcements:
1) Push feature is now temporarily disabled, sorry for that. We will enable it within 24 hours. No application update will be needed.
2) Windows Live Messenger (formerly known as MSN) service support has been removed due to Microsoft Marketplace request. Hopefully, we will be able to add it back some time soon.
We appreciate your interest in beta round.Please send us all your comments and suggestions.

Daniel mentioned in his video that push notifications weren't working, and now we know why! The service was disabled on the back end, but has been turned back on:

"Great news! Push notifications are now functional. Please re-connect with your accounts."

Also, the folks at Shape verified that Microsoft asked them to remove WLM support. Not terribly surprising, but it's nice to know we were right on both counts! (If you are looking for this post, it is comment number 75 on the 'AAAAND, IT'S FINALLY HERE!' post)

Source: IM+ Facebook Page