Peace Walker bored the piss out of me so I never beat it. I didn't miss much either. SFLS was great for the story, but if you couldn't sit through it then you weren't a real Syphon Filter fan in the first place.
I kinda feel the same way metal gear seems the same like in portable ops I was like the ninja again lame. PW demo didn't intrest me so I didn't buy it. SF and splinter cell seem to always bring something new to the table. I like dark mirror I gotta get LS yet. For Restistance better than I epected anyway.