Eames is jumping all over the place in the Snow Fortress. He falls all the time. Jumping onto baddies on snow machines, leaping from the fortress away from grenades, etc.
If falling in your dream state is a “kick”, how come that didn't knock Eames out of it. If it doesn't, then how come the fortress explosion didn't kick Cobb out of Limbo? And why did Ari have to jump out the window? If that didn't “kick” her she'd have fallen to her death and stayed in Limbo forever.
Most troubling is that Cobb says they can't stay in Fischer's dream for a week, or they'll get killed by his subconsciousness. He says “I guarantee it.” So what did they do for a week in Cobb's dream on the flight? He doesn't get up till they're approaching LA, so did the stewardess “kick” them or what? Did they have a week long dream battle we never see? And if they were only in the Van/Rain dream for about an hour or two, why did they need a 10 hour flight? Wouldn't a quick nap in his office sufficed? Did they need that long to sedate him properly?
For a film many considered too “high minded” for an average movie goer, there are some basic issues that could have been solved with a few throw away lines.

Level 5 is incorrect. Cobb and Ariadne go to sleep with a dreammachine so level 5 is their shared state, I'm guessing Cobb is the dreamer. Ariadne gets a kick that takes her up a level, Cobb remains and eventually loses himself in Limbo and subsequently rambles onto an old Saito. You can see that he is a bit confused and straining to remember something while speaking with Saito, not as lucid as previously.

It's only implied that Cobb and Saito shoot themselves… but that may not have been the case. It could be that they simply waited for Limbo to “end” — and the time ran out on their sedative and they woke up. That would explain the abruptness of the end.

Only one “level” really exists – the first, and that’s Cobb’s dream state! The scene where we’re introduced to the people who are almost permamently sleeping -where sleep is the reality for them, hints at where Cobb is really at -the first (or even possibly the limbo) state. The fact that the token is never seen to fall at the end confirms it. Also, there are more important life issues to consider, so I’ll leave you with that!

Err, nevermind. I meant level 6.

To answer your first question – I don’t believe that receiving a kick while awake in the current level dream state, will awaken you. You either need to die within that dream, or receive a kick from the previous dream level. In Limbo, they’d have to jump out the window to not receive a kick, but to die.

Exactly. This is the problem I had. The van is a kick to get them out of the Hotel Level (and presumably, Cobb and Saito have to invent kicks to get all the way back up to the “Van Level”). It’s explained that Cobb and Saito spend the majority of the time in Limbo, so they wouldn’t spend the week in the Van Level (but their bodies would have been underwater, which doesn’t fit with the other members using an oxygen tank). So did the team stay a week in the Van Level? No, because they are clearly awake before the flight lands, and so presumably did not spend the whole ten hours asleep. But HOW did they get a kick back to reality?