Sights Passes: Venice; Rome Florence

If your focus on your Roma segment is Vatican City, you should know that while Vatican City is surrounded by Roma, it is an independent country. Rome buses , metro and trams approach the edges of Vatican City but none enter it. None of the attractions - most specifically the Vatican Museums - are covered by the Roma Pass because it is only for the city of Roma.

If you consider using the Roma Pass you need to do the arithmetic and see if it really saves you money. The clock starts on that pass the first time you use it - be that for transportation or a museum or other attraction - and that the days are calendar days ending at midnight (not 24 hour days), so if you first use it for a bus at 9pm you only get 3 hours for that day.

Which museums would you like to visit in Venice? I usually use a Chorus Pass if I will visit many Chorus churches on a visit. Almost all the art is in situ in the various churches, only a few of the churches charge. Only a few are in the Chorus plan.

Rome: just my 2-cents here but skip the Omnia pass, which is the only one offering skip-the-line to the Vatican museums/St Peters. At € 98,00, you'd be hard pressed to make it pay off…if price value is important to you.
That pass is a combo of Omnia entries (religious sites) and Roma Pass, and includes some things better skipped, IMHO (St Peter's Prison, Christiana Hoho). We also didn't use public transit enough over our several visits to Rome to have made the price worthwhile: it was much less expensive just to buy a few individual tickets for the occasional hop.

You can easily get skip-the-line benefits at the Vatican museums/Sistine by buying timed-entry tickets (€20) directly from their website:

http://mv.vatican.va/3_EN/pages/MV_Home.html

For €37 you can book a 3-hour tour of both the museums and the basilica through that same site. As the museums are vast and a tour allows direct access to the basilica, this can be well worth the price.

For everything else, you might consider the Roma Pass - although, as with any pass, you need to have the time and interest in what it covers to make it worthwhile. Do note that that the 48-hour version only allows free access to a single attraction, and the 3-day version to two with small price reductions on anything else. I wouldn't purchase it merely for line-skipping as that can easily be gotten around at the Colosseum: the only attraction besides the Vatican with long ticket queues. And even with the pass, advance reservations must be made for Galleria Borghese by phone if you wish to use it for that one.

As Nigel has pointed out, the churches in Rome are stuffed with oodles of art, and almost all of them are free: no need for a pass to enjoy them.

The excellent pass we used in Florence (Amici degli Uffizi) is sadly no longer the value that it was, and I can't weigh in on the Firenze Pass.

The only pass I always get is a vaporetto pass in Venice. Even when I plan on walking everywhere, I find the convenience of being able to hop on the boat at the end of a long day to be wonderful. I also enjoy just going on random rides on the vaporetti, with no particular end point – I've discovered some wonderful places that way. With the high cost of individual tickets, the pass pays for itself easily.

The pass I used to use in Florence has changed and is no longer worth it. Instead, I just make reservations at the Ufizzi and the Academia, to avoid the lines. Make those reservations well ahead of time, particularly if you're traveling in high season or shoulder season. The other museums are inexpensive and typically don't have lines. However, if you want to see the Scrovegni chapel, reservations are a good idea, although in my experience you don't need to make them long in advance.

In Rome and the Vatican I also go with individual reservations. Definitely make them for the Vatican museums to avoid the lines. Also, if you want to see the Borghese gallery, which is amazing, reservations are the only way to get in. Definitely make Vatican and Borghese reservations ahead of time.