Has anyone taken tours from Viator while they were in Rome, either around the city or outside day trips?
Yes, I did. Viator is a consolidator and sells you off to a service provider you could have booked directly yourself. I had lots of problems with Viator in Rome and also in other destinations and don't use them now other than to refer to what might be available.
Thank you for the advice, I will not be booking with them. Would you recommend a day trip down the Amalfi Coast or into Tuscany region with another group?
Both areas are too far to be considered a day trip. You might want to do them as an overnight. Donna