I really, really don't think Wash's death was 'just for shock factor'. I'd say that's a cop out excuse, really. Wash's death DOES serve a purpose, albiet one that may very well be setting up something more in the series(movies, TV, whatever). With Wash's death, you change characters.
EVERYONE becomes different after that, and then the risk goes up 100% when you realize that these people are not immune like most heroes in stories are. Not only does it push the risk factor up and heighten tension, but it also means that Zoe, Mal, et all will be extremely different people afterwards. Sure, we don't have much of an afterwards(which is why it feels like a good set up for more), but what we DO have is the fight where you really see this effect and change its had on people.
It DID have meaning, but not in the same direct way that Book's death did.
Honestly, though, I'm glad Joss isn't afraid to kill characters. Too often in movies the main characters are immune to death. Its become too common over the years and it makes watching movies far too predictable. That risk of death is something that isn't so common these days, and its a breath of fresh air. In fact, I think its one of the BEST parts about the movie which really makes it stand out.