I've played a few (4 and a half) games of Neptune's Pride, now. It's a pretty slow-paced long-term diplomacy/risk-like online flash game. Lots of people have reviewed it, some of them discussing obvious strategy.
The following are nuances regarding the game's mechanics; things I wish I could have found on some nerd's blog like the Arm Chair Empire, but instead had to find out the hard way.
The game has timers on ticks
With a tick every 10 minutes by default. Every tick in the game, jump preps countdown and fleets move. ETAs are reported in approximate units of time because of this.
Payday times shift later over time
Probably because there are 144 ticks in a day, but additional time is used to compute locations before the next delay. This happens because the delay loop PROBABLY does this: compute stuff, wait 600 seconds, repeat... rather than this: check clock, compute stuff, check clock again and find difference in number of seconds, wait 600-minus-that-difference seconds.
Fleets arriving on the same tick fight as one fleet
So if you're OCD enough, you can have fleets from two different systems timed to arrive on the same tick at a system, and will be considered one fleet.
During a tick, fleets leave before they land
This means that a fleet leaving with an ETA of ~30 minutes will evade a fleet landing in ~30 minutes, however, a fleet leaving with an ETA of ~30 minutes will not evade a fleet landing in ~20 minutes.
Fleet speeds and ETAs are recalculated mid-flight when speed tech advances
This is pretty deadly if you depend on ETAs of fleets to arrive at a system in order to form a defense.