VoIP and push notifications (e.g. Skype): consumer experience?

Can one really get a good VoIP experience when Push Notifications is used to wake up the B-party app?
Let's take the Skype case.
It seems they have made changes to their plans over the course of this year.
At least what Skype says so, in February the story was:

The company noted that some other VoIP clients on Windows Phone can jump-start into the foreground when a call comes in using the standard push notification system (which Microsoft has had in place since the original release of Windows Phone 7), but that this wouldn't work for Skype — they say it takes too long to process the notification, open the app, and set up the call to make it practical. On iOS and Android, Skype is able to keep its agent running whether the app is in the foreground or not, which allows calls to ring immediately.

But now, Skype is utilising Push notifications.

Last week, if you recall, Microsoft announced Skype for Windows 8, a touch-friendly app that appeared in the Windows Store the same day Win 8 went on sale. Now, with Windows Phone 8 getting its big reveal, the company is following up with a WP8 version, which Microsoft says is coming soon. Like the new Windows 8 app, it runs in the background, delivering push notifications even when you're looking at something else. 

Emerging Issue 1: 

How is a VoIP (realtime) service consumer experience impacted by Push Notifications?

If A wants to contact B over e.g. Skype, then if Skype is not in foreground in B's device, there needs to be a wake-up by the push notification.
Then, the app is activated, and then the actual call setup signaling starts. 

All this may slow down the response times experienced by the consumer.

Emerging Issue2: 

What if one is roaming abroad? For the consumer this is typically expensive and she would prefer wifi.

Now I many Push Notifications systems use the cellular channel only.
What if roaming is off? No way for incoming calls if the VoIP app is not in the foreground?

There are a couple of possible reasons why e.g. MS/Skype has designed it this way. 

First one is the battery consumption. From that point of view, it makes sense to have Skype in the background of course, rather than refreshing itself continuously.
But the VoIP apps in some other systems, e.g. Symbian could reside as default in the foreground with quite good battery times.

Second one I have heard is that Windows Phone 8 is not a genuinely multitasking OS or rather, the multitasking services are open to first party apps only. 

WPCentral got the word from a source they trust that this improved multitasking will only work for 1st party apps. To take advantage of this functionality 3rd party developers will have to use a small hack and list their apps as " GPS apps". However it's not clear if this will influence the certification process, which it might.

Of course it is easy to come up with conspriracy theories also, especially in the Skype case.
One is that operators have been concerned of Skype and MS combination taking the call revenues. It can be argued that push notifications create less load on the networks (but how relevant that is in 3G coverage needed for Skype?) and therefore operators have in essence ensured that the circuit-switched call remains the primary means of communications in Windows Phone devices.

Comments welcomed. Will be keen to check out how VoIP apps utilising Push Notifications perform.