How long to get through customs, rent a car in Dublin?

Thanks. But what about all the airport and car rental stuff? Any idea how long that'll take?

It could be anything--there is really no predicting what kind of line you'll get for either. Check to see if your rental agency offers any kind of priority lane for pickup. I'd count on about an hour to account for any hiccups.

Customs is nothing. Just a walk through. Immigration can take a little longer depending on how crowded it is. Maybe an hour. Again, the car rental is the same. If first in line, pretty quick and if tenth it may take awhile. Set aside a couple of hours to do everything.

Thanks!

I'd give myself 2.5 hours from the time the plane lands (wheels down, not gate arrival time) to when I think I'll be in the rental car. I believe the 8:45 arrival time is actually wheels down. So you need to add another 15 minutes to taxi to the gate and 15 minutes to get off the plane and to walk to passport control. An hour for passport control, another 15 minutes to shuttle to the car rental location and another 30-45 minutes to get your car. Trim is about 30-45 minutes from the airport.

As was mentioned, if you 're enrolled in one of the company membership programs (Hertz Gold, etc) then you'll be able to bypass the line, proceed directly to your car, and be on your way with a minimum of delay.
If you'll need to join the queue at the rental car desk then all bets are off - could take a long time indeed if things are moving slowly.
Might be worth joining the Elite Member program for your particular company just to expedite things a bit.