Arriving at FCO at 10PM - Best Place to Stay??

You'll need some time to get through passport control and to collect your luggage. That late, after the grueling flight from the west coast ( you are talking about La Canada CA, aren't you?), I'd bite the bullet and go right over to the Hilton.

Check out the Hilton Garden Inn which is kind of off site, but does have a shuttle.

The Hilton offers discounts - sometimes BIG discounts if you prepay. That means you loose your money if you have to change your plans. But our travel agent got them down to $147 a night (TA's can be good at things like that with the international chains. We ended up adding a night and actually had two seperate reservations. But at check in they combined them and we did not have to checkout and recheckin.

Robert, I've got a similar situation. Flying into FCO late from Sicily, then the next day just relaxing and seeing Ostia Antica, and then flying out from FCO for the US the 2nd morning. I didn't want to go into central Rome since we'll be there earlier in the trip. I finally decided on Seccy Hotel in Fiumicino. Keep in mind I haven't stayed there yet, but it looks like a great place-- and much better rates than the American-branded hotels at/near the airport.

Consider taking the express train to Termini for 11E per person, getting a decent room within 3 blocks of the station (hundreds to choose from ) and taking the express train to Florence the next morning. Advantages include saving about $200.00 in lodging and the need to get a rental car.

First, thanks to everyone who has posted to date!

In terms of the suggestions to catch the train from FCO to Termini, is that practical at what's likely to be 11PM by the time we clear customs, get our bags, etc.?

Assuming yes (and that feels like a big assumption), and assuming the best way out of Rome is via train and not car, what would be a practical stopping point via train from Rome en route to Siena? (we are not heading to Florence on this trip -- staying "local" the whole time in Tuscany + CT only)

Thanks again!

In Rome the past 2 times we've flown into it there has been no time at all to clear customs/immigration; get off the plane and walk out of the airport thru the door marked "non-EU" (assuming you're traveling with carry-on luggage). It isn't the long wait like in the US.