Please, I've used Rome's Metro successfully. But I will be in Rome with an older lady friend with arthritic knees. Any elevators or escalators??? Cannot remember.
There are escalators in at least some, but I remember them being a little spotty about state of repair... sometimes out of commission. When I traveled in Rome with someone with some mobility challenges, I found taxis to be a real blessing... that way the walking could be saved for touring, rather than getting there. You might check the Ron in Rome website to see if it has information on accessibility in Rome.
Lea, My memory is a bit "foggy" on that topic, but I vaguely recall both Escalators and stairs, at least at Roma Termini. At many of the other stations, there were only stairs. Will you be using rail stations as well? Changing trains and platforms often involves a trip down into a tunnel and then back up to the next platform. In many cases, only stairs are provided (although occasionally there will be a ramp and/or an elevator). Good luck!
wikipedia has information on each metro station for example: http://en.wikipedia.org/wiki/Spagna_(Rome_Metro) Look under the heading: Services. However, the equiptment might not work. Also, there is an elevator from Spagna metro exit to near the top of the Spainish Steps. Caution, there are still steps, just not 144 of them. Look behind the McDonald's Have fun and take breaks!
I have no problem with stairs, but I still made little use of the Rome Metro. The buses are usually as convenient if not more so, and for someone with mobility problems, you will want some taxis too (particularly if she can't stand for long periods - you can NEVER count on getting a seat on a Roman bus). The only place where the Metro really was handy was EUR. I loved the "Square Colosseum," but the area is hardly a must-see for most people.