If this is about multitasking or background apps, I'm all for it. I do that--or want to do that--all the time.
If it's about that 15 minutes you can upload to the internet, it's massively disappointing. I could see Sony's OS burning a gig easily. I really couldn't see them using 3.5 GB. Microsoft does crap like that.
Likely, the reason is that Sony didn't want to offer too much more RAM than Microsoft because they thought it would be unused. As OS function, you know it's going to be used.