The one thing that I have learned after years of traveling both for work and pleasure is the mantra:
WHEN IN DOUBT-GO OR DO OR BUY IT! You always have more regrets about "not doing" when you could have. Trust me when I say, Rome will take your breath away.....I fly there everyweek for work and it still amazes me! I spent a term in college studying French and Italian Art in Florence and I will admit that I much prefer Rome to Florence and Siena.Besides,do what you heart tells you to do-you know,that little voice inside of you? You won't regret it!

I agree 100% with dutyfree and other posters that tell you to go for it!

I have done Florence as a day trip from Rome so I don't see why viceversa wouldn't work. And the Eurostar is such a comfortable way to do it so, why not? As long as you don't try to go crazy once you're there. Just "stop and smell the flowers".
Rome is my favorite city in the world. I have been there 9 times and I don't think I could be in Italy and not go to Rome at least for a day. One time we were in a Med cruise and took the bus from Civitavecchia at least to spend 6 hrs in Rome! I never regreted it.

I am definitely going to go for it!!! Thanks guys