Watching 24 is like injecting heroine. As soon as you're done, you need more.
Tonight's episode was a big deal just because of the involvement of certain characters that fans have come to know and take a lot of interest in over the past few seasons. The ending was one of those "Holy shit!" moments that you just don't get on TV, and with the next twist in the final five or six hours, it can only get more crazy.
Get the previous seasons on DVD. You won't be disappointed. I don't even watch that much TV, and yet, I can't live without this one.