I will be flying with EasyJet from Paris - Rome in early April.
I haven't flew any with them, I am choosing easyJet as it is a lot cheaper than Vueling and there seem be more times for me to choose from. I have asked people about easyJet on this forum, most of them seem not to have any problem with the airline.
However Vueling uses Fiumicino, and this seems to be an easier airport to get to as there are trains to get there from Rome city centre, but it is further away from the city. Ciampino has no train station, therefore you would need to use buses.
Hope this help, and I am sure the experienced flyers will come in soon and give better advice.