I think that question is very hard to answer without spoilers.  You have to read or watch and make that decision for yourself.  I would argue it is worth it, but we may differ.

Ah, thank you! :)

Mean Volantine?  Unless you meant Valryian, in which case that "tart" lived this day.

I don't know, Martin has mentioned that the book and show will differ, much like Jago dying in season one and still living in the books.  They could easily introduce a new character for the show or rework a character (like they did Loras...poorly).   I will wait and see on that issue.

In one move Tywin Lannister just completely obliterated his most powerful enemy and secured the entire North because of Tyrion's marriage to Sansa. Quite frankly, he would have been stupid to do anything else.

You classify that as "no reason"?

Rather more significantly, I don't believe any mention was made of Jon Snow being Robb's heir in the show, so I guess we can throw that out too (not that it was ever especially likely that anything would come of it).

No, and I didn't think of that. Still, that's more of a reason for Tywin to kill those characters off and not a reason for the writers to, if you know what I mean. I'm taking a wait and see approach now to see if this'll spawn some interesting plot lines. 

Tywin Lannister is consistently described as a ruthless and extremely intelligent man. He doesn't care about "guest right", he cares about winning his war at any cost, preferably the least cost to his own family possible.

Now if this whole thing had been organised by Lysa Arryn or something, you would have a point. But the Red Wedding fits perfectly into the characters of Tywin, Walder Frey and Robb.

Ok, sure, I guess I'm just pissed that so much momentum was built and I was waiting for him to do some epic shit for ages, and now I'll get nothing from him or his army. 

I find Arya's story to be much more interesting, so if this significantly adds to her plotline then I am 100% for it.

Great episode last night, I havnt read the books so i wasnt expecting it and could not see that coming, ill admit it stunned me bigtime, even during today at work ive been thinking of it (so that is the sign of a excellent series).
Im gutted and sort of not at the same time. Im gutted because i did like Catelyn and Robb Stark and would of liked them to survive, but at the same time it made the best TV ive ever watched.
Im really interested to see where this takes the story now, Robb was the one of the Lannisters main rivals but not the biggest. The fact that Daenerys Targaryen is creating the biggest army westeros will ever see backed with 3 fire breathing dragons will make them standup and notice, infact im almost convinced that she will get the iron throne back in her name, i dont think theres anybody that can beat her now. And then you have everybody elses stories going on  like the rest of the stark kids, jon snow, gendry and stannis with the red witch! man i love this show :)