So you have a round every ten pulses or whatever it was decided on (there was a thread that entered mud mechanics, I think Elhe was the one who stated the code factored in 10 or 12 pulses a round?). For the sake of argument, we'll assume 10: That means after ten pulses, you have another round of combat on the next pulse.
Trip will succeed and lag you for twice the number of pulses it takes for a round to arrive. This means you are guaranteed to have two rounds of combat go past. We'll say 20 pulses for argument. Meaning if you trip literally on the pulse that the round goes by, your next command will be on the same pulse two rounds later (ignoring things like ping, etc).
If the lag is 1.5 rounds, that's 15 pulses. It could be that if you trip just after a round, you'll reach about 10 pulses and have one round of combat. You've then only got 5 pulses of lag left. This isn't enough for another round of combat to arrive, so you can get a command.
If you attempt the skill, say, 4 pulses before the next round of combat then the round comes (down to 11 pulses) and then by the time the next round is calculated, you've still got 1 pulse of lag left. Your command goes quickly in after 2 rounds of combat.
That's how it works with 1.5 rounds of lag. It's possible that you'll see 2 rounds of combat pass, or 1. Maybe even get two trips in three rounds of combat. But I guarantee the trip after that, will see 2 rounds of combat pass regardless of your speed.
Legsweep is 10 pulses or 1 round. This means you're guaranteed another attempt much quicker than trip.
Yhorian