Expo is 10 minutes away from the metro station, you can easily walk from there. Bib pick-up was quick and easy. Being the most important half marathon in Italy, I expected the expo to have more things to offer, but it wasn't bad. Small detail: race t-shirts were too small.
You can take the metro to the start line, everything was running smoothly the morning of the race. There are trucks to leave your bags, taking them to the finish line. The only thing I think could be improved is the availability of portable toilets before the race, I spent at least 25 minutes waiting and it was full of people doing their thing on the trees.
Start was good, not too crowded as I had imagined so the waves worked-out well. Race course is linear but with hills, be prepared for that. Not many people cheering in the streets but if you know Rome, it's nice to see the street (Cristoforo Colombo) empty, something that doesn't happen often. Water stations every 5 km as in any Italian run, with water in the first one, water and salts in the second one, water and orange slices in the third. At the finish line, there were many things to eat/drink (you could get a gelato this year) and a massage tent. They give you a kind of poncho to cover from the wind since you are on the seaside.
To go back to Rome, there's the train less than 5 minutes away from the finish line. It was crowded but, for Rome standards, surprisingly very well organized. Remember to buy your ticket in advance and you can avoid the long lines in the ticket machine.
Can't wait to do it again next year!