Best app for reminders (with dates)?

I'm currently at University, and I'm looking for the best iPhone app to add reminders with due dates, so I can keep track of my assignments / tests due etc.

Preferably, I would like something like 'Clear', but I want to be able to add due dates (so I know what's down the list etc).

I was using the stock reminders app, but I find the syncing terrible. Many things I've ticked off on my phone stay unticked on my computer for ages, and many things that I've ticked off on my computer stay on my phone for a long time. It gets quite frustrating when you go to tick something off the list that you've done, but since it takes a good few minutes to properly sync, it ticks off something that you haven't done and occasionally you don't realise.

I want it to be able to send reminder as well. I want to be able to specify a due date, and then set reminders to perhaps five days before, and then maybe another one three days before.

I know this has probably been discussed to death, but I still haven't found a satisfying alternative.

Thanks.