Hi Tom. Here's a link to the "Rome Transport" thread:
http://www.flyertalk.com/forum/showt...eferrerid=9641
I recommended M.L.M. last year after a bad experience with LimoServiceRome. Scan the thread and you'll find details.
It's €35 plus a late night/early morning supplement. I know the €35 is still current (Elia has billboards all over - was just there 2 weeks ago) but the €10 supplement could have changed since last February). A cab theoretically would cost you the same - if you don't get taken for that proverbial ride...
Buona fortuna e buon viaggio.