One tip, from someone who enjoys the upper deck - if landing at airports known for slow immigration (for example, MIA), then make damn sure you bolt down the stairs as soon as the seatbelt signs are off.
Technically, FIRST should be allowed off, then Club World (what you are if you're on the upper deck), then World Traveller Plus, then World Traveller (Economy).
In reality, what usually happens if the layout downstairs is First, WT+, CW, WT, is that First and WT+ manage to get off and into the immigration queue before you've had a chance to pick your stuff from the overhead lockers. It's important that you get to the foot of the stairs as soon as is possible.