24 - a beginners guide

[matt]

okay - i watched season one and really enjoyed it up to about midday but then got really bored/disinterested when they kept repeating storylines in the second half. saw it out until the end but then haven't bothered watching any more until the new one (we're up to episode 4 here in the uk and i'm enjoying it so far)

anyway, my question is this: which, if any, of the seasons i've missed should i catch up on - all of them, none of them, some of them..?