OK so i play alot of street fighter 4 but lately the games mechanincs are begining to bug me a little and i'm thinking of picking up this and giving it a fair whack but dont really know what its all about. 
 
i'v seen the evo replays and whatched a fair amount of tutorials but it still doesnt let me know what it comes down to.  so if any one out there can help me, how does this game differ from sf4? is there crouch teching and reversal moves? ive heard that its based more around using your normal moves for defense and fireballs are near useless.

anyway if someone can help me out and explain what all the fuss to do with third strike is based on i would really appreciate it! thanx!

its different, it has a parrying system and a few other things.  Look just play the demo and see what you think.

Its way harder than sf4 and its super hype with other people.

It's primarily a poking game and less on the more combo like nature of SF4. 
 
Confirmed a hit? Shoryu! For example...

There are still reversal moves, they're been around since SF2, IIRC. Fireballs are indeed less useful due to parrying preventing even chip damage, and over all Third Strike favors careful play without overextending yourself too much. I always like to say it's the fighting game most like actual fighting, minus the shooting fireballs, robots, and stretchy-armed rubber men. 
 
EDIT: I should actually say it's the 2D fighting game most like actual fighting.

just got through the demo with ryu and dudley and i have to say this game is fuckin awesome i've never played a fighter that has such a natural feel to it. god damn parrying is hard tho!! 
 
i need to learn me some dudley skills beside his st.fp and target combo lol

I think the mind games are just intense. I got into a good Ryu vs Ryu fight online, and I got some good stuff in and parried almost all of his Hadokens, the last round he didnt throw one, but he just ran up on me and just bodied me. You have to focus and just wait for an opening.