Hmm I'm not sure if the regular XMB interface is going to allow you to do things like meet up in a group and hop into different games together. That is the real question on my mind. Can you do everything out side of home if you don't want to access the virtual world?
Home will undergo beta this April, so we will know for sure, and Sony should have time to address it (if not already).
For now, you can gather in the in-game lobbies (and hop from 1 game to another). Home is only GA in fall, so the online games have to be pretty standalone by design.
The way I see if it you're going to go to the trouble of creating an avatar based world, why let people access the same features outside?
As long as they have quick navigation/teleportation and short load time, I wouldn't complain if Sony takes this approach. Without PS Home, the in-game lobbies need to be loaded anyway.
Also, from what I see this is just basically an application sitting on top of the PSN framework. What's to stop MS from copying this by making their own app that sits on the xbox live frame work that does the same thing? it's like booting up your console and choosing "Graphical" or "text based" interface.
May be a moot point in the long run because the argument is recursive. MS will do whatever they deem best. Sony has started its momentum going today.
Wanted to re-watch the trailers. The gametrailer site is down. Are there mirrors ?
EDIT: Ok, Gradthrawn's and Synergy34's posts already address Tap In and Qroach's concerns