Make sure at the beginning of the trip there are enough guides, and also don't let them push you to stay together, it shouldn't matter.
Make sure your boots are fully waterproofed before going as it's impossible to dry anything. Also I would've taken 2 pairs of thin gloves, one for everyday use that may get wet and another as liners for summit.
The toilet tent can be difficult to negotiate in pitch black over rocks, so be prepared!.
11 out of 12 of us took Diamox and we had little/no altitude sickness and made summit quite easily, sure the longer route helped too, but seeing some sick people being taken down, we were pleased we took all precautions.
We took a small flip HD video camera which was great - and it took AA batteries so no charging worries.
Loads of wet wipes! - they give you a bowl of water but difficult to use it in the cramped tent.
Take a sigg type bottle as well as camelback, useful as a hot water bottle, extra fluid on long days and in case camelback freezes on summit night
Dyrolite is useful even if you don't get ill, it replaces salts so helps hydration